Make client report a newer version number to the server than 2011-07-31 does and make the server enforce it

Speed up periodical map unloading by moving beginSave() and endSave() to outer loop in Map::timerUpdate()

Fix some texture stuff: remove item_fence.png, use fence.png, remove inexisting cactus.png from texture atlas (replace with nothing because cactus is rare)

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

* The map will reside in world/map.sqlite
* It will load from the sectors folder but will not save there

* I didn't understand that expression last fix and now the furnace would burn fuel
even when it had no source item.

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

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

Some access violations and segfaults and strange behaviour might have
been caused by this.

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

If a block has (at least visible) liquids, the block below should also
be flowed in.

See explanation in http://2pktfkt.de/irc/minetest-delta/2011-08-22.html

This is just a chat window with the / text pre-loaded.