Constify keycode and move the static array of localizable names from the
guiKeyChangeMenu header to the implementation file, changing its name.

commands:
/#ipban <nick>
/#ipunban <ip>

Marking *.cpp files as C++ files makes for nicer diffs when using
--color-words or similar options.

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

Collect the player's eye position coding in a Player method, and
use it in client to pass the eye position information to the game.

This is currently only used in the lighting update for remote
players in client.

This quiets a warning in Clang.

At least two reasons for this:
* activeKey is treated as signed (check for sign, assign -1, etc)
* the ID retrieved from Irrlicht's events are signed