Move RPATH flags out of Platform/AIX.cmake into platform-specific
compiler information files Platform/AIX-XL and Platform/AIX-GNU.
The flags need to be set for each compiler of each language.
This moves GNU compiler flags into new-style modules
Compiler/GNU-<lang>.cmake
Platform/<os>-GNU-<lang>.cmake
We use language-independent helper modules
Compiler/GNU.cmake
Platform/<os>-GNU.cmake
to define macros consolidating the information.
Brad King
Todd Gamblin