Fix <rdar://problem/6619539> incompatible pointer types sending 'XCElementSpacer *', expected 'XCElement *' (not handling protocol signatures correctly?).

- Reworked ASTContext::canAssignObjCInterfaces().
- Added ObjCProtocolDecl::lookupProtocolNamed().



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@65773 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed