tge.c: Section the file.
tge.c: Import messages.
tge.c: Add have_required_items and item definitions.
tge.c: Add bitmap_font, plot_single_glyph, plot_glyph and screenlocstring_plot.
tge.c: expand_object: Drop unreferenced variable.
tge.c: Add get_next_scanline.
tge.c: Make tile_t a struct of tile rows, rather than an array.
tge.c: Add is_door_open.
tge.c: State required by is_door_open.