[splittiming] Define far ahead version.

This will let other branches develop .ssc if needed
while this branch takes its time.

src/NotesLoaderSSC.h

@@ -25,6 +25,8 @@ enum SSCLoadingStates
 const float VERSION_RADAR_FAKE = 0.53f;
 /** @brief The version where WarpSegments started to be utilized. */
 const float VERSION_WARP_SEGMENT = 0.56f;
+/** @brief The version that formally introduced Split Timing. */
+const float VERSION_SPLIT_TIMING = 0.7f;
 
 /**
  * @brief The SSCLoader handles all of the parsing needed for .ssc files.