Rename attributes:

Rename attributes:
'objc_ownership_cfretain' -> 'cf_ownership_retain'
'objc_ownership_cfrelease' -> 'cf_ownership_release'

Motivation: Core Foundation objects can be used in isolation from Objective-C,
and this forces users to reason about the separate semantics of CF objects. More
Sema support pending.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@70884 91177308-0d34-0410-b5e6-96231b3b80d8