Merging r339667:

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r339667 | theraven | 2018-08-14 12:04:36 +0200 (Tue, 14 Aug 2018) | 11 lines

Add a stub mangling for ObjC selectors in the Microsoft ABI.

This mangling is used only for outlined SEH finally blocks, which have
internal linkage.

This fixes the failure of CodeGenObjC/2007-04-03-ObjcEH.m on builds with
expensive checks enabled, on Windows.  This test should probably be
specifying a triple: it currently picks up whatever the host environment
is using.  Unfortunately, I have no idea what it is trying to test,
because it contains no comments and predates Clang having working
Objective-C IR generation.
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_70@340437 91177308-0d34-0410-b5e6-96231b3b80d8