[Ohrrpgce] wip r13879: Update spriteset import to support variable frame counts

[cron at rpg.hamsterrepublic.com]

https://github.com/ohrrpgce/ohrrpgce/commit/b711df982f2d11b144233ecb2c2643cbd4c265ac
Author: teeemcee <teeemcee at 7d344553-34f0-0310-a9b1-970ce8f1c3a2>
Date:   Fri Apr 11 01:43:27 2025 +0000

    Update spriteset import to support variable frame counts
    
    This is still only a half solution. Need a new import/export format which
    indicates how the spritesheet should be split into frames.
    The number of frames can't be changed during import. Existing frameids are kept.
    

 common.rbas    |  2 +-
 custom_udts.bi |  2 ++
 drawing.bas    | 63 ++++++++++++++++++++++++++++++++++++++++++----------------
 loading.rbas   |  9 +++++++--
 whatsnew.txt   |  2 ++
 5 files changed, 58 insertions(+), 20 deletions(-)