Merging r143871:

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r143871 | chandlerc | 2011-11-06 01:39:46 -0800 (Sun, 06 Nov 2011) | 3 lines

Lift the GCCVersion type into the header file and start persisting it in
the detected GCC installation. This allows us to expose another aspect
of what we detected: the GCC version. This will be used shortly.
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llvm-svn: 143948