This introduces `def_script_pointers`, `def_text_pointers`, and `object_const_def` macros, and applies them to all maps. Most other map labels have also been identified.
All graphics are now png.
Some files were split out of necessity:
- gfx/trade.2bpp -> gfx/game_boy.norepeat.png gfx/link_cable.png
- gfx/red/introfight.2bpp -> gfx/red/intro_nido_{1,2,3}.6x6.png
- gfx/blue/introfight.2bpp -> gfx/blue/intro_purin_{1,2,3}.6x6.png
