Misc: Make struct member functions file-local

src/core/game_list.cpp

@@ -36,6 +36,8 @@ Log_SetChannel(GameList);
 #endif
 
 namespace GameList {
+namespace {
+
 enum : u32
 {
   GAME_LIST_CACHE_SIGNATURE = 0x45434C47,
@@ -54,6 +56,8 @@ struct PlayedTimeEntry
   std::time_t total_played_time;
 };
 
+} // namespace
+
 using CacheMap = PreferUnorderedStringMap<Entry>;
 using PlayedTimeMap = PreferUnorderedStringMap<PlayedTimeEntry>;