cellSaveData* improvements

* cellSaveDataFixedSave2 and cellSaveDataFixedLoad2 implemented. Still a
little buggy.
* Small fix the cellSaveDataList(Save|Load)2 problem in Disgaea D2 and
other games.

NOTE: cellSysutil_SaveData.cpp is a total mess: some blocks of code
appear in all the syscalls. I just want to wait until most of the
SaveData functions are implemented and working to do some serious
refactoring.