Fix ObjC @encode for C++ classes w/virtual bases.

PR17142.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190912 91177308-0d34-0410-b5e6-96231b3b80d8
Fix accepts-invalid if a variable template explicit instantiation is missing an
argument list, but could be instantiated with argument list of <>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190913 91177308-0d34-0410-b5e6-96231b3b80d8