ExtWarn/Warnings. Mostly the name of the warning was changed to match the semantics, but in the PR20356 cases, the warning was about valid code, so the diagnostic was changed from ExtWarn to Warning instead. llvm-svn: 213443
<rdar://problem/12061922> llvm-svn: 163772
These will warn under -Wformat-non-iso, and will still be rejected outright on other platforms. <rdar://problem/12061922> llvm-svn: 163771