[analyzer] Path-insensitive checker for writes into an auto-releasing pointer

from the wrong auto-releasing pool, as such writes may crash.

rdar://25301111

Differential Revision: https://reviews.llvm.org/D44722

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@328827 91177308-0d34-0410-b5e6-96231b3b80d8