Merging r324439:
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r324439 | compnerd | 2018-02-07 02:55:08 +0100 (Wed, 07 Feb 2018) | 5 lines

AST: support SwiftCC on MS ABI

Microsoft has reserved the identifier 'S' as the swift calling
convention.  Decorate the symbols appropriately.  This enables swift on
Windows.
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llvm-svn: 324460
2 files changed