Sema: Enforce C++11 pointer-to-member template arguments should rules

The standard is pretty clear on what it allows inside of template
arguments for non-type template parameters of pointer-to-member.

They must be of the form &qualified-id and cannot come from sources like
constexpr VarDecls or things of that nature.

This fixes PR18192.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196852 91177308-0d34-0410-b5e6-96231b3b80d8
Fix via-file-asm test failure on windows

The windows target does not support using an external assembler so
the test case was failing with this error:

error: there is no external assembler that can be used on this platform

The test was updated to always explicitly pass a target that has
both an interal and external assembler.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@196854 91177308-0d34-0410-b5e6-96231b3b80d8