* Set OS-specific default compilers

* Fix flake8 warnings

* Use code from the `distro` package to improve linux distro detection.

Various issues [1] [2] with the platform.linux_distribution function led
to the function being deprecated in python 3.4. The pipi package distro
[3] contains compatible improved code that better tracks current methods
for identifying linux distributions (see, for example, [4],[5]).

[1]: https://bugs.python.org/issue20454
[2]: http://bugs.python.org/issue1322
[3]: https://pypi.python.org/pypi/distro
[4]: https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/lsbrelease.html
[5]: https://www.freedesktop.org/software/systemd/man/os-release.html

* fix (potential) unicode problems

* libSplash: Add 1.6.0 Release

Add the latest release of libSplash, version 1.6.0.

* Fix flake8 checks (another loop inversion issue)

* module files tutorial : first complete draft

- first complete draft for module files tutorial
- minor corrections to module file reference

* module file tutorial : first batch of corrections

- module avail spelled out fully
- typos from @adamjstewart
- rewording of a few sentences

* module file tutorial : first batch of corrections

- emphasized lines in yaml files

* module file tutorial : fixes according to @citibeth and @adamjstewart reviews

- used long format for command options
- reworded unclear sentence on tokes
- reworked table in reference manual to make it clearer

* module file tutorial : implemented corrections collected on site from @schlyfts

* module file tutorial : removed comment (@hartzell suggestion)

* updates to matio package

- update to a AutoTools package
- add variants for hdf5 and zlib
- add latest version

* fix flake8 error

* fix and simplify opencoarrays package using new CMakePackge methods

* add new version

* Add options for hashes, tree depth, and YAML to `spack spec`.

- Can now display hashes with `spack spec`, like `spack find`.
  - Removed the old "ids" argument to `spack spec` (which
    printed numerical values)b

- Can output YAML spec from `spack spec` with `-y`

- Can control depth of DAG traversal with --cover=[nodes|edges|paths]

- Can print install status (installed, missing, not installed) with -I

* Don't use YAML aliases in specs.

- Force Spack's YAML dumper to ignore aliases.
- aliases cause non-canonical YAML to be used in DAG hash, and result in
  redundant hashes.
- add a test to ensure this behavior stays

* fix to trilinos package

* fix to dealii package

* fix to everytrace package

* fix to everytrace-example package

* changes suggested by @davydden

* remove obsolete instructions on hacking clang+gfortran

* add detailed instructions on how to setup Clang+gfortran on macOS

* spack install: forward sys.stdin to child processes fixes #2140

 - [ ] redirection process is spawned in __enter__ instead of __init__
 - [ ] sys.stdin is forwarded to child processes

* log: wrapped __init__ definition

* In order to use TAU module, we have to set TAU_MAKEFILE env variable.

* updated with suggestions from @citibeth

* Fix style checker bug.

* spack flake8: print cwd-relative paths by default, with root-relative option.

1) list gfortran as a fc and f77 compiler that can work with clang
2) allow compatible gfortran to ./spack compiler find with clang by matching version numbers

This is based on the discussions in

https://github.com/LLNL/spack/issues/237
https://github.com/dealii/dealii/wiki/deal.II-in-Spack#mixing-gcc-and-clang-on-osx

This is not a long term solution but something to get us through the next months until the compiler
infrastructure is reworked to allow mixing and matching for C/C++ and Fortran compilers

Funded-by: IDEAS
Project: IDEAS/xSDK
Time: 1.5 hours

Without GRIB2 and HDF-EOS support yet.

* works to build newest version of nmap with gcc@5.3.0

* formatting

* clean up

- Detailed debug information is now handed back to the parent process
  from builds, for *any* type of exception.

- previously this only worked for Spack ProcessErrors, but now it works
  for any type of error raised in a child.

- Spack will print an error message and source code context for build
  errors by default.

- It will print a stack trace when using `spack -d`, even when the error
  occurred in the child process.

- Ported old run-flake8-tests qa script to `spack flake8` command.
- New command does not modify files in the source tree
- Copies files to a temp stage modifies them there, and runs tests.
- Updated docs and `run-flake8-tests` script to call `spack flake8`.

- generalized and fixed to work with any key in YAML file
- simplified schema writing, as well
- add more unit tests for the config system
- Rename test/yaml.py to test/spack_yaml.py
  - Add test/yaml.pyc to ignored pyc files.

- Added new preferences to config.yaml:
  - source_cache
  - misc_cache
  - verify_ssl
  - checksum
  - dirty

- Moved temp finding logic to spack.stage
- Updated stage tests
- Added tests for new path substaitution of $user, $spack, $tempdir

- Added a schema for config.yaml
- Moved install tree configuration to config.yaml
- Moved etc/spack/install.yaml to etc/spack/defaults/config.yaml
- renamed install_area to "store", to use a term in common with guix/nix.
  - in `config.yaml` file, it's called the `install_tree` to be more
    intuitive to users.
  - `install_tree` might've worked in the code, but `install_tree` is
    already a global function in the spack namespace, from
    llnl.util.filesystem.

Merge #2030 added a cyclic dependency between the Cray platform needing
to read a `targets.yaml` config file and `config.py` needing to get the
platform names.

This commit removes the cyclic dependency in favor of the more general
config scheme. It also removes the now functionless `targets.yaml`
config file. This breaks 'frontend' targets on the Cray platform but
all architecture targets, including the frontend, that are provided by
CrayPE are added to the Platform anyway so users can be explicit about
the architecture targeted by the Cray compiler wrappers:

```
spack spec libelf arch=cray-CNL-frontend
```

becomes

```
spack spec libelf arch=cray-CNL-mc8         # on an XK7 or
spack spec libelf arch=cray-CNL-sandybridge # on an older XC30, etc..
```

The only way the 'frontend' target can be defined after this commit is
through target environment variables.

On MacOS, brew installs /usr/local/bin/python but the Python prefix is not /usr/local/bin
Use the python command sys.exec to get the correct directory, instead of the ad hoc self.prefix
previously used

This was a bear to debug; been driving me nuts since I started using spack.
Since spack passes PYTHONHOME down to package builds in the environment
it was passing PYTHONHOME of /usr/local/bin to the PETSc build that uses Python so
the PETSc Python ./configure errored immediately with

ImportError: No module named site

since python could find no python modules. Todd Gamblin pointed out that my first try to fix
this was wrong since it assumed the spack python was the same python used to run spack. Elizabeth Fischer
suggested how to get it to work also with python3

Funded-by: IDEAS
Project: IDEAS/xSDK
Time:  7 hours
Thanks-to: Todd Gamblin, Elizabeth Fischer