Compile additional source files passed to build into itsown static library.
This resolves problem when using this function within a multithreaded make invoked call.
  -- This might be a bug in CMake...
Make get_output_status and get_output more robust.
You can now also send in a list of commands
Add check for installed dolfin
Add a hash of the instant directory to generated tmp dir. Also only remove these
tmp directories preventing instant-clean to remove other directories which it shouldn't.
Merge branch 'fix-issue-2'
Merge branch 'fix-dolfin-16'