Commit a bit of a hack to fully handle the situation where variables are

Commit a bit of a hack to fully handle the situation where variables are
marked explicitly as uninitialized through direct self initialization:

  int x = x;

With r128894 we prevented warnings about this code, and this patch
teaches the analysis engine to continue analyzing subsequent uses of
'x'. This should wrap up PR9624.

There is still an open question of whether we should suppress the
maybe-uninitialized warnings resulting from variables initialized in
this fashion. The definitely-uninitialized uses should always be warned.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128932 91177308-0d34-0410-b5e6-96231b3b80d8