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

Some compilers complain when a class is declared as a struct or vice
versa. Fix by making sure that the correct tag is used both in
declaration and definition.

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

Made wielded tool move slightly (and smoothly) during view bobbing. Making the tool be a child node of an empty scene node instead of the camera scene node seemingly fixed the uncontrollable tool jitter, too.

Collected and moved existing camera infrastructure from game.cpp to camera.cpp and camera.h. Introduced configuration settings 'fov' which chooses the camera's (vertical) field of view and 'view_bobbing' which currently does nothing. Other code refactored to not expect the FOV to be a build time constant.