Fixes water display issues.
Fix primary secondary tertiary colour sprites
Swapped variable names to match game
Added notes to draw_sprite
Cleaned up obsolete variables
Removed redundant comments about not being tested
Zoomed land working.
Added zoom_masks
Zooming working again. Graphical glitch along x=0 line.
Tidy viewport code
Fixed zoom bug.
Merge pull request #277 from duncanspumpkin/fix_gfx

Fix gfx