[Whistler]

I've found this in Q1 engine code:

 	if (in_speed.state & 1)
 		speed = cl_movespeedkey.value;
 	else
 		speed = 1;

...and about the cl_movespeedkey thing:

 cvar_t	cl_movespeedkey = {"cl_movespeedkey","2.0"};

Note: the shift key in Quake1 is speed UP (not speed down) which is different from HL.

In CS the default value of cl_movespeedkey CVAR is usually 0.52, but the plain HL is 0.3. For each MOD you can type "cl_movespeedkey" in the console and you'll get the value. Note you can't use CVAR_GET_FLOAT("cl_movespeedkey") in the bot code because this CVAR is client-side.