Switch the license to be LGPLv2/later, with small parts still remaining as GPLv2/later, by agreement of major contributors

Inventory menu (with dragging) improved. Crafting is now handled via a IACTION_CRAFT inventory action.

Inventory menu changes: Tooltips; dragging; drop from menu. Lag is a bit annoying (even in single player).

The huge item definition and item namespace unification patch (itemdef), see http://c55.me/minetest/wiki/doku.php?id=changes:itemdef

Also contains some commented-out code for testing out different looks
in the future.

This allows us to map the keys which are not considered in
irrlicht's EKEY_CODE system, such as \, [, /, ] etc.