[PATCH] These builtin functions set errno. Mark them accordingly.

[Chandler Carruth]

I'm not really a fan of this. I don't know why it is reasonable to expect the builtin to set errno. If you want the libc behavior of a libc function, you should call the libc function. My impression was that one of the primary reasons for the existence of these builtins was to *avoid* calling a libc function.

http://reviews.llvm.org/D3806