Merging r279268:

Merging r279268:
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r279268 | majnemer | 2016-08-19 09:37:40 -0700 (Fri, 19 Aug 2016) | 5 lines

[CloneFunction] Don't remove unrelated nodes from the CGSSC

CGSCC use a WeakVH to track call sites.  RAUW a call within a function
can result in that WeakVH getting confused about whether or not the call
site is still around.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_39@279477 91177308-0d34-0410-b5e6-96231b3b80d8