Merging r196145:

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r196145 | mren | 2013-12-02 12:10:37 -0800 (Mon, 02 Dec 2013) | 5 lines

Debug Info: Move the constant for Debug Info Version from Dwarf.h to Metadata.h.

Suggested by Eric.
Paired commit with r196144.

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llvm-svn: 196820