* Fixed some issues with CUDA-Intel compiler conflicts.

* Comment about expressing CUDA-compiler conflicts.

* More precise conflicts and also add support for Intel 19.0

* record conflicts with compiler versions which don't provide
  required c++ standard support
* add doxygen (build) dependency
* add note that range-v3 is header-only as of 0.3.6 and update
  package description

Makes building of documentation optional.

Use environment variables to point setup.py to Spack installations
of hdf5/netcdf

We add new variants to handle readline vs libedit, a client-only
build and install, and bindings to TCL, Python and Perl. We also add
new versions and the ability to detect remote versions not otherwise
dealt with.

Elmer finite element method solver; builds Elmer, ElmerICE and
contributed solvers with MPI support.

This avoids using a system-installed CUDA package. In the future a
variant can be added to allow using Spack-installed CUDA, but for
now CUDA support is always disabled.

Added a variant to allow conduit to build with newer versions of
HDF5.  Set the default for the variant to prefer compatibility mode
with HDF5 v1.8

- disable sundials varaiant for dealii and mfem - as they are incomatible with sundials@4.1.0

- add a patch to fix build error with superlu-dist

* Added a package for chapel.

* flake8 compliance.

* serialize the F90 interface build

* serialize the F90 interface build

* netgen: update broken URL

* netgen: fix url_for_version URL

openfoam-com needs flex's FlexLexer.h, which can only be found if flex
is also a link dependency.

Patch extracted from #7536 courtesy of @mgsternberg

* update R to v3.5.3