Signed-off-by: Stephan Bergmann <sbergman@redhat.com>:
* added clucene-config-MINGW-atomic.h, to not lose _CL_HAVE_GCC_ATOMIC_FUNCTIONS
  when applicable there
* renamed clucene-config-GCC.h to clucene-config-GCC-atomic.h for consistency
  with above

Change-Id: I3dd15721b568fa9358b79ec28bad39249200c773