graphics/darktable: Update to 2.2.2
Use devel/openmp to provide OpenMP runtime instead of the entire LLVM
(submitted by mandree@). This allows to use LLVM 3.9 at build time,
without fearing any dependency to multiple LLVM versions at runtime
(Mesa pulls LLVM 3.7 for instance).
Change COMPILER_TYPE to CHOSEN_COMPILER_TYPE, (submitted by
mandree@). This was blocking bug 199098.
Include the following patch from upstream, which fixes a regression
(suggested by upstream):