old_craft_grid, craft_inv) and
minetest.register_craft_predict(itemstack, player, old_craft_grid,
craft_inv)

This not only makes the vector functions faster, but also makes them more
consistent with other functions.

Instead of collecting all objects within a huge radius (which could be
a big value), just register each player that connects and give back the
current hold list.

Texture names must now be escaped in formspec elements image[],
background[], image_button[], image_button_exit[].

Instead of special-case handling of texture loading (and unloading
which was missing) in guiFormSpecMenu.cpp, use the newly created
ISimpleTextureSource interface which is a minimal subset of
ITextureSource. There is an implementation of this interface
used by GUIEngine (MenuTextureSource).

Fix an off-by-one bug in unescape_string; it caused requests for a
texture called "\0".