* app/tile.c
	* app/tile.h
	* app/tile_manager.c
	* app/tile_swap.c:

	Allocate Tile's array of TileRowHints dynamically.  Make type
	of TileRowHint explicit since it's fairly space-critical.
	Can save several hundred K of memory with this and struct
	changes.

	Added warnings for old basically-untested-or-insane
	paths through the tile referencing code.

	* app/tile_pvt.h: Shrink down and rearrange fields of Tile
	struct to save some space with gcc's padding for most people.

	* app/paint_funcs.c: Use tile_sanitize_rowhints() to ensure
          that rowhints have been allocated before use.

	* app/channel_ops.c
	* app/gdisplay.c
	* app/pixel_region.c: Cosmetic, sanity or unfinished debug
          changes (the latter commented out) for fun and reference.