server: Release atoms when destroying a window class.

dlls/user32/tests/class.c

@@ -115,6 +115,8 @@ static void ClassTest(HINSTANCE hInstance, BOOL global)
         return;
     ok(classatom, "failed to register class\n");
 
+    ok(GetClipboardFormatNameW(classatom, str, ARRAY_SIZE(str)) != 0, "atom not found\n");
+
     ok(!RegisterClassW (&cls),
         "RegisterClass of the same class should fail for the second time\n");
 
@@ -230,6 +232,8 @@ static void ClassTest(HINSTANCE hInstance, BOOL global)
     ok(UnregisterClassW(className, hInstance),
         "UnregisterClass() failed\n");
 
+    ok(GetClipboardFormatNameW(classatom, str, ARRAY_SIZE(str)) == 0,
+        "atom still found\n");
     return;
 }
 

server/class.c

@@ -76,6 +76,8 @@ static struct window_class *create_class( struct process *process, int extra_byt
 
 static void destroy_class( struct window_class *class )
 {
+    release_global_atom( NULL, class->atom );
+    release_global_atom( NULL, class->base_atom );
     list_remove( &class->entry );
     release_object( class->process );
     free( class );