Provide stop-gap solution to crash reported in PR 14436.

Provide stop-gap solution to crash reported in PR 14436.

This was also covered by <rdar://problem/12753384>.  The static analyzer
evaluates a CXXConstructExpr within an initializer expression and
RegionStore doesn't know how to handle the resulting CXXTempObjectRegion
that gets created.  We need a better solution than just dropping the
value, but we need to better understand how to implement the right
semantics here.

Thanks to Jordan for his help diagnosing the behavior here.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168741 91177308-0d34-0410-b5e6-96231b3b80d8