an Objective-C declaration
This commit ensures that Sema won't enter a C++ declarator scope when the
current context is an Objective-C declaration. This prevents an assertion
failure in EnterDeclaratorContext that's used to ensure that current context
will be restored correctly after exiting the declarator context.
rdar://20560175
Differential Revision: https://reviews.llvm.org/D26922
llvm-svn: 288893