[Sema] UsingShadowDecl shouldn't be hidden by the UsingDecl that owns it

rdar://23454249

Differential Revision: https://reviews.llvm.org/D28514

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@292805 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit f40cbc811c47dc9890ea845536f003371ea7d771)
2 files changed