PGO: Separate out common isMachO logic; no functionality change

<rdar://problem/15943240>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204297 91177308-0d34-0410-b5e6-96231b3b80d8
scanf format checking: include the buffer length in the fix-it for %s.

Patch by Zach Davis!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@204300 91177308-0d34-0410-b5e6-96231b3b80d8