Merge r309917 into 5.0 -- Fix leaking diagnostics from headers

[llvmbot]

Bugzilla Link	34039
Resolution	FIXED
Resolved on	Aug 03, 2017 09:34
Version	unspecified
OS	Windows NT
Blocks	#33196
Reporter	LLVM Bugzilla Contributor
CC	@zmodem,@mclow

Extended Description

r309917 should be merged into the 5.0 release branch. Otherwise there is a regression where C++11 extension warnings are leaked from libc++ headers in C++03 mode.

[llvmbot]

@​Marshall can you OK this merge?

[mclow]

This is fine with me.

[zmodem]

r309958.