Extend the tests for -Wmissing-variable-declarations.

We shouldn't throw a warning when the static keyword is not present in
an anonymous namespace, just like we do for -Wmissing-prototypes.

llvm-svn: 290443

clang/test/SemaCXX/warn-missing-variable-declarations.cpp

@@ -47,3 +47,8 @@ class C {
     static int x = 0; // no-warn
   }
 };
+
+// There is also no need to use static in anonymous namespaces.
+namespace {
+  int vgood4;
+}