[analyzer] Use the CFG to see if a constructor is for a local variable.

Previously we were using ParentMap and crawling through the parent DeclStmt.
This should be at least slightly cheaper (and is also more flexible).

No (intended) functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160807 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed