Revert "Revert r184787: "Added arm_neon intrinsic tests.""

This reverts commit r184817. The failure Chandler was seeing was most likely the
bug that Bob Wilson fixed in r184870 (which was a bug caught by these tests).

To be safe, I just checked again on x86-64 mac os x/linux that this test passed
(which it did).

llvm-svn: 185110