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

Remove stuff made obsolete by making players more ActiveObject-like and raise protocol version number by one (because it is not compatible at all anymore)

strict_protocol_version_checking setting; PROTOCOL_VERSION in clientserver.h; clean up defaultsettings.cpp and minetest.conf.example

-- TOCLIENT_OBJECTDATA: peer ID field is missing
-- TOCLIENT_ACTIVE_OBJECT_REMOVE_ADD: added: init length should be u32, not u16

This is done with the new TOSERVER_PLAYERITEM message, that informs the
server on the index of the wielded item.

--HG--
extra : rebase_source : 7260636295d9068fbeeddf4143c89f2b8a91446c

--HG--
extra : rebase_source : e8ec407f60711d42d33be4811b2880088f617b5b