[ObjC][Modules] Don't perform property lookup in hidden class extensions

rdar://30603803

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@295903 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit b10bb3222f717f6181b0fc845870dbbf4d1c429d)
3 files changed