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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    llvm-svn: 294479