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

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

inventorycube: use all three specified textures; also moved mesh creation / modification functions to mesh.cpp; in lua, inventorycube is now called minetest.inventorycube

Make camera.cpp Irrlicht 1.8-compatible by calling ITexture::lock differently depending on the irrlicht version.

Fix single-frame lag in camera yaw/pitch, tune view bobbing and add wielded tool movement when walking and tweak stuff a bit

Simplistic wielded tool lighting, added setMeshVerticesColor to utility.h and refactored some other code into calls of that

Create a separate scene manager for the wielded tool. This fixes the glitchyness in large map coordinates and some depth buffer problems. (The tool doesn't bob anymore when walking, this will be fixed later.) Fix MSVC build (thanks to dannydark).

Convert any inventory item into a mesh, bring back InventoryItem::getImageRay(), some const-correctness fixes