Fix handling of condition variables in the face of temp dtors.

The assignment needs to be before the destruction of the temporary.
This patch calls out to addStmt, which invokes VisitDeclStmt, which has
all the correct logic for handling temporaries.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207985 91177308-0d34-0410-b5e6-96231b3b80d8