Introduce and document a new objc_returns_inner_pointer
attribute, and consume it by performing a retain+autorelease
on message receivers when they're not immediately loaded from
an object with precise lifetime.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135764 91177308-0d34-0410-b5e6-96231b3b80d8