compiler flag fixes

compiler flag fixes

- added patched Check{C,CXX}CompilerFlag.cmake scripts to enable invalid
  option detection with Intel Compilers 12.x; the patches have been
  submitted to CMake (will be included in 2.8.9:
  http://cmake.org/gitweb?p=cmake.git;a=commit;h=bbb895959f54a9dec9f5132313f4a71fafc458e5),
  these files should be removed when the required CMake version will
  contain the fixes
- moved compiler option generation after the default cmake variable
  setting to add -Wunknown-pragmas only when GMX_OPENMP=OFF
- moved optimization options to release flags
- enabled warnings with the Intel Compilers

Change-Id: I767aea7f043255ee95eef5e7cb597c1c99feb05a