Move duplicate uninitialized warning suppression into the

AnalysisBasedWarnings Sema layer and out of the Analysis library itself.
This returns the uninitialized values analysis to a more pure form,
allowing its original logic to correctly detect some categories of
definitely uninitialized values. Fixes PR10358 (again).

Thanks to Ted for reviewing and updating this patch after his rewrite of
several portions of this analysis.

llvm-svn: 135748