Previously, when the CSM restriction 'LOAD_CLIENT_MODS' was used a
client was still able to add CSM code to 'builtin' to bypass that
restriction, because 'builtin' is not yet verified.
Until server-sent CSM and verifying of 'builtin' are complete, make
'LOAD_CLIENT_MODS' disable the loading of builtin.
Clarify code comments and messages to distinguish between client-side
modding and client-side scripting. 'Scripting' includes 'builtin',
'modding' does not.
In pitch fly mode, you fly to the exact direction you are pointing at, using the forward key. Other move directions are also pitched accordingly.
It allows smoother and more complex movements.
Can be enabled/disabled by L key by default (set keymap_pitchfly in minetest.conf)
