Move some of the logic about classifying Objective-C methods into

Move some of the logic about classifying Objective-C methods into
conventional categories into Basic and AST.  Update the self-init checker
to use this logic;  CFRefCountChecker is complicated enough that I didn't
want to touch it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@126817 91177308-0d34-0410-b5e6-96231b3b80d8