[PATCH] Sema: Implement DR244

[David Majnemer]

================
Comment at: lib/Sema/SemaExprCXX.cpp:136-137
@@ -135,4 +135,4 @@
     //
     //   the class-names are looked up as types in the scope designated by
     //   the nested-name-specifier.
     //
----------------
Richard Smith wrote:
> Please update this to match the standard (in particular, "the second class-name is looked up in the same scope as the first").
Done. :)

================
Comment at: test/CXX/drs/dr2xx.cpp:1016
@@ -1015,3 +1015,2 @@
   B::A() {} // ok
-  C::~C() {} // expected-error {{expected the class name}}
   C::~A() {} // ok
----------------
Richard Smith wrote:
> Why was this deleted? If we no longer reject this, that's a regression, and we can no longer claim to implement DR298...
It was deleted because it conflicts with the following line. Not only do we still reject, we provide a superior diagnostic :)

I've updated the test-case so that we test both cases.

http://reviews.llvm.org/D3583