PNGwriter, libSplash: Add `master` version (#1744)

* PNGwriter, libSplash: Add `master` version

* PNGwriter, libSplash: Add `dev` versions

Can be used for now, `develop` is currently discouraged.

var/spack/repos/builtin/packages/libsplash/package.py

@@ -37,6 +37,10 @@ class Libsplash(Package):
     homepage = "https://github.com/ComputationalRadiationPhysics/libSplash"
     url      = "https://github.com/ComputationalRadiationPhysics/libSplash/archive/v1.4.0.tar.gz"
 
+    version('dev', branch='dev',
+            git='https://github.com/ComputationalRadiationPhysics/libSplash.git')
+    version('master', branch='master',
+            git='https://github.com/ComputationalRadiationPhysics/libSplash.git')
     version('1.4.0', '2de37bcef6fafa1960391bf44b1b50e0')
     version('1.3.1', '524580ba088d97253d03b4611772f37c')
     version('1.2.4', '3fccb314293d22966beb7afd83b746d0')

var/spack/repos/builtin/packages/pngwriter/package.py

@@ -38,6 +38,10 @@ class Pngwriter(Package):
     homepage = "http://pngwriter.sourceforge.net/"
     url      = "https://github.com/pngwriter/pngwriter/archive/0.5.6.tar.gz"
 
+    version('dev', branch='dev',
+            git='https://github.com/pngwriter/pngwriter.git')
+    version('master', branch='master',
+            git='https://github.com/pngwriter/pngwriter.git')
     version('0.5.6', 'c13bd1fdc0e331a246e6127b5f262136')
 
     depends_on('cmake', type='build')