Alternate Fire.
its just +button3, its not affecting anything really. some people have stuff like
alias +button3 "homing on; +attack"
alias -button3 "homing off; wait; wait; -attack"
well now, i just made +button3 an actual button like in q3. homing on/off lasersight on/off still works. oh and i made nonhoming sk's, fast rails, and impact grenade launchers.
all this stuff can be disabled tho with g_allowalternate 0/1 set at the server.
