c++: global-namespace-qualified var after class def [PR90107]

Here we wrongly reject the definition of "::N::a"

  struct A;
  namespace N { extern A a; }
  struct A {} ::N::a;

because our code to diagnose a missing ; after a class definition doesn't
realize that :: can follow a class definition.

	PR c++/90107

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_class_specifier_1): Accept :: after a class
	definition.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/qualified6.C: New test.

gcc/cp/parser.cc

@@ -25933,6 +25933,7 @@ cp_parser_class_specifier_1 (cp_parser* parser)
       case CPP_OPEN_PAREN:
       case CPP_CLOSE_PAREN:
       case CPP_COMMA:
+      case CPP_SCOPE:
         want_semicolon = false;
         break;

gcc/testsuite/g++.dg/parse/qualified6.C

+// PR c++/90107
+// { dg-do compile }
+
+struct A;
+namespace N { extern A a; }
+struct A {} ::N::a;
+
+struct A1;
+struct B { static A1 a1; };
+struct A1 {} ::B::a1;