[analyzer] Suppress warnings coming out of std::basic_string.

The analyzer cannot reason about the internal invariances of the data structure (radar://15194597).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194004 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Track the count of NSOrderedSet similarly to other fast enumerations.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194005 91177308-0d34-0410-b5e6-96231b3b80d8