Merging r292949:

Merging r292949:
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r292949 | rnk | 2017-01-24 08:57:55 -0800 (Tue, 24 Jan 2017) | 6 lines

[CodeView] Fix off-by-one error in def range gap emission

Also fixes a much worse bug where we emitted the wrong gap size for the
def range uncovered by the test for this issue.

Fixes PR31726.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@294479 91177308-0d34-0410-b5e6-96231b3b80d8