RecursivelyDeleteTriviallyDeadInstructions() could remove
more than 1 instruction. The caller need to be aware of this
and adjust instruction iterators accordingly.

rdar://16679376

Repaired r207302.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207309 91177308-0d34-0410-b5e6-96231b3b80d8