[analyzer] Support for OSObjects out parameters in RetainCountChecker

rdar://46357478
rdar://47121327

Differential Revision: https://reviews.llvm.org/D56240

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@350982 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed