Merging r287353:

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r287353 | hans | 2016-11-18 09:33:05 -0800 (Fri, 18 Nov 2016) | 12 lines

IRMover: Avoid accidentally mapping types from the destination module (PR30799)

During Module linking, it's possible for SrcM->getIdentifiedStructTypes();
to return types that are actually defined in the destination module
(DstM). Depending on how the bitcode file was read,
getIdentifiedStructTypes() might do a walk over all values, including
metadata nodes, looking for types. In my case, a debug info metadata
node was shared between the two modules, and it referred to a type
defined in the destination module (see test case).

Differential Revision: https://reviews.llvm.org/D26212

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llvm-svn: 287906