Qt: Add option to reset played time

src/frontend-common/game_list.h

@@ -81,6 +81,7 @@ void Refresh(bool invalidate_cache, bool only_cache = false, ProgressCallback* p
 
 /// Add played time for the specified serial.
 void AddPlayedTimeForSerial(const std::string& serial, std::time_t last_time, std::time_t add_time);
+void ClearPlayedTimeForSerial(const std::string& serial);
 
 /// Returns the total time played for a game. Requires the game to be scanned in the list.
 std::time_t GetCachedPlayedTimeForSerial(const std::string& serial);