Merging r294318:

Merging r294318:
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r294318 | adrian | 2017-02-07 09:35:41 -0800 (Tue, 07 Feb 2017) | 12 lines

Fix the bitcode upgrade for DIGlobalVariable in a DIImportedEntity context.

The bitcode upgrade for DIGlobalVariable unconditionally wrapped
DIGlobalVariables in a DIGlobalVariableExpression. When a
DIGlobalVariable is referenced by a DIImportedEntity, however, this is
wrong. This patch fixes the bitcode upgrade by deferring the creation
of DIGlobalVariableExpressions until we know the context of the
DIGlobalVariable.

<rdar://problem/30134279>

Differential Revision: https://reviews.llvm.org/D29349
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@294352 91177308-0d34-0410-b5e6-96231b3b80d8