Removing some more unnecessary manual quotes from attribute diagnostics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198387 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Don't track return value of NSNull +null for retain/release tracking.

Fixes <rdar://problem/12858915>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198388 91177308-0d34-0410-b5e6-96231b3b80d8