No longer truncate savegame version in gamelog.

Add an extended feature for changed savegame format.

src/saveload/extended_ver_sl.h

@@ -45,6 +45,7 @@ enum SlXvFeatureIndex {
 	XSLFI_TEMPLATE_REPLACEMENT,                   ///< Template-based train replacement
 	XSLFI_MORE_RAIL_TYPES,                        ///< Increased number of rail types
 	XSLFI_CARGO_TYPE_ORDERS,                      ///< Cargo-specific load/unload order flags
+	XSLFI_EXTENDED_GAMELOG,                       ///< Extended gamelog
 
 	XSLFI_RIFF_HEADER_60_BIT,                     ///< Size field in RIFF chunk header is 60 bit
 	XSLFI_HEIGHT_8_BIT,                           ///< Map tile height is 8 bit instead of 4 bit, but savegame version may be before this became true in trunk