)
Values signal handler is called with:
	AL = signal number (see #01793)
	AH = signal argument
Return: RETF, CF set: terminate process
	RETF, CF clear, ZF set: abort any interrupted system call with an error
	RETF, CF clear, ZF clear: restart any interrupted system call
	IRET: restart any interrupted system call
Note:	the signal handler may also perform a nonlocal GOTO by resetting the
	  stack pointer and jumping; before doing so, it should dismiss the
	  signal by calling this function with BL=04h