r237769 - [OPENMP] -fopenmp enables OpenMP support (fix for http://llvm.org/PR23492)

[Jack Howarth]

     Why is it necessary to switch back the -fopenmp default rather
than just have your users invoke -fopenmp=libgomp if they want to
continue using a non-functional OpenMP under clang? Certainly at this
point the focus should be encouraging testing of the new llvm openmp
library to identify corner cases that are still broken in the OpenMP
3.1 support promised for the 3.7 release. The openmp maintainers have
been quite responsive to fixing this issues when reported on
bugzilla...

https://llvm.org/bugs/show_bug.cgi?id=23387
https://llvm.org/bugs/show_bug.cgi?id=23392

Also switching the default isn't really the best way to nudge along
the proposed the library name change to libomp if that really was the
underlying impetus of this commit.
        Jack
ps What exactly is the utility of building non-functional openmp
support with libgomp anyway? It seems rather pointless to enable
openmp support in software if the generated code doesn't actually
exercise its functionality.