Move returning to pause menu code to separate function

This code is getting a bit more complicated now, we should maybe stop
copy-pasting it everywhere.

desktop_version/src/Game.cpp

@@ -7755,3 +7755,11 @@ void Game::returntoeditor()
     map.scrolldir = 0;
 }
 #endif
+
+void Game::returntopausemenu()
+{
+    ingame_titlemode = false;
+    returntomenu(kludge_ingametemp);
+    gamestate = MAPMODE;
+    map.kludge_to_bg();
+}