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

IRespawnInitiator and InventoryActions are abstract classes, but they
were missing a virtual destructor. Define it, even if it does nothing
and its absence most likely makes no difference other tha causing
warnings during compile.

Make ToolItem and MaterialItem to convert names by aliases at creation time too (necessary for eg. crafting)

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.

Do not assert if count becomes larger than getStackMax() in InventoryItem::add(); it is nicer for scripting and overall hacking this way, because rising it higher than the limit is does not break anything. It should be, and is, enforced elsewhere where appropriate.

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

And some simple animation when trying to dig...

Also, the temp item wasn't being deleted, might have been a memory leak.
Now you will only eat 1 item off a stack

This one contains these changes from main c55:
* Adds a function to check if there is room for a specific item
* Using that, you can now pick up rats if you have a full inventory and a not full rat stack
* Furnace would cook only 1 item if that item used the last available result slot, now it will continue
* Furnace will say it's overloaded
* Furnace won't wait until the next step to start on the next item
 - This caused small fuels to cook slower than meant to
 - Also caused furnaces to say they were out of fuel after finishing the last fuel item