Mark DR1250 as implemented

We implemented this DR back in r258768 but forgot to mark it as
implemented.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@259335 91177308-0d34-0410-b5e6-96231b3b80d8

test/CXX/drs/dr12xx.cpp

+// RUN: %clang_cc1 -std=c++98 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++11 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++14 %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+// RUN: %clang_cc1 -std=c++1z %s -verify -fexceptions -fcxx-exceptions -pedantic-errors
+
+// expected-no-diagnostics
+
+namespace dr1250 {  // dr1250: 3.9
+struct Incomplete;
+
+struct Base {
+  virtual const Incomplete *meow() = 0;
+};
+
+struct Derived : Base {
+  virtual Incomplete *meow();
+};
+} // dr1250

test/SemaCXX/virtual-override.cpp

@@ -289,15 +289,3 @@ namespace PR8168 {
     static void foo() {} // expected-error{{'static' member function 'foo' overrides a virtual function}}
   };
 }
-
-namespace PR26297 {
-struct Incomplete;
-
-struct Base {
-  virtual const Incomplete *meow() = 0;
-};
-
-struct Derived : Base {
-  virtual Incomplete *meow() override { return nullptr; }
-};
-}

www/cxx_dr_status.html

@@ -7315,7 +7315,7 @@ and <I>POD class</I></td>
     <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1250">1250</a></td>
     <td>CD3</td>
     <td>Cv-qualification of incomplete virtual function return types</td>
-    <td class="none" align="center">Unknown</td>
+    <td class="svn" align="center">SVN</td>
   </tr>
   <tr id="1251">
     <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1251">1251</a></td>