Change large amount of objects to be configurable via a setting in minetest.conf (max_objects_per_block).

* If client count is unbearable, immediately delete denied clients
* Re-prioritize the checking order of things about incoming clients
* Remove a huge CPU-wasting exception in ReliablePacketBuffer

Lessen the sky color glitch when quickly turning to look up after looking at ground that contains caves

Fix params number

Add pressed texture name

Fix string def

Fix syntax error

Add old style mod selection in worldconfig dialog