Repair 2010-05-31-palignr.c test

This test was silently failing since a long time because it failed to include
stdlib.h (as it's running in a freestanding environment). However, because we
 used just not clang_cc1 instead of the verify mode, this regression was never
 noticed and the test was just always passing.

This adds -ffreestanding to the invocation, so that tmmintrin.h doesn't
indirectly include mm_malloc.h, which in turns includes the unavailable stdlib.h.
We also run now in the -verify mode to prevent that we silently regress again.

I've also updated the test to no longer check the return value of _mm_alignr_epi8
as this is also causing it to fail (and it's not really the job of this test to
test this).


Patch by Raphael Isemann (D34022)

llvm-svn: 305089