Allow objc_requires_super to be used to check class methods as well.

Also, unify ObjCShouldCallSuperDealloc and ObjCShouldCallSuperFinalize.
The two have identical behavior and will never be active at the same time.

There's one last simplification now, which is that if we see a call to
[super foo] and we are currently in a method named 'foo', we will
/unconditionally/ clear the ObjCShouldCallSuper flag, rather than check
first to see if we're in a method where calling super is required. There's
no reason to pay the extra lookup price here.

llvm-svn: 166285