Only add this attribute when it's set. If it's not there, the assumption is that it's off.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@189064 91177308-0d34-0410-b5e6-96231b3b80d8
Check for absence of the flag.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@189069 91177308-0d34-0410-b5e6-96231b3b80d8
ObjectiveC migrator: some refactoring to reduce
code size.


git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@189070 91177308-0d34-0410-b5e6-96231b3b80d8