Merging r196809:
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r196809 | rsmith | 2013-12-09 11:52:39 -0800 (Mon, 09 Dec 2013) | 2 lines

Unbreak build by adding an implementation of PopStackFrames function.

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git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/branches/release_34@197010 91177308-0d34-0410-b5e6-96231b3b80d8