Objective-C arc: don't count use of __weak
variables when they are used in such unevaluated 
contexts as __typeof, etc. // rdar://13942025


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182423 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer; alternated edges] look through expressions just like Environment does.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182425 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer;alternate edges] prune out extra edges to a subexpression where we dive-in and out of a subexpression.

Fixes <rdar://problem/13941891>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182426 91177308-0d34-0410-b5e6-96231b3b80d8