[objc-arc] Added an option to arc-annotations for turning off CheckForCFGHazard.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179717 91177308-0d34-0410-b5e6-96231b3b80d8
[objc-arc] Added descriptions for EnableARCAnnotations, EnableCheckForCFGHazards, EnableARCOptimizations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179718 91177308-0d34-0410-b5e6-96231b3b80d8