INT 21 - Novell NetWare - SYNCHRONIZATION SERVICES - WAIT ON SEMAPHORE          
	AX = C502h
	CX:DX = semaphore handle
	BP = timeout limit in timer ticks (1/18 sec)
		0000h return immediately if semaphore already zero or negative
Return: AL = status
	    00h successful
	    FEh timeout
	    FFh invalid handle
Desc:	decrement the semaphore's value, optionally waiting until its value
	  becomes positive before decrementing
Note:	this function is supported by NetWare 4.6+, Advanced NetWare 1.0+, and
	  Alloy NTNX
SeeAlso: AX=C500h"NetWare",AX=C501h,AX=C503h,AX=F220h/SF=02h