OS X: Split Intel compiler information files

Create platform information modules Platform/Darwin-Intel-(C|CXX).cmake
and helper module Platform/Darwin-Intel.cmake.  Teach existing module
Platform/Darwin-Intel-Fortran.cmake to use the helper too.  Move
information from Platform/Darwin-icc.cmake into these files and drop
information already in Platform/Darwin.cmake to avoid duplication.
Merge topic 'osx-intel-info-split' into next

3693c63f OS X: Split Intel compiler information files