Change to the VM SPec

[bobrow]

On page p 95, the top, add an alternatibve to "Save sufficient information ..."
as
"or, if the implementation allows immediate interrupts, call
INTERRUPT[NIL;NIL;2]
which will print 
Interrupted below <name of function interrupted>
and cause a break with BRKEXP = NIL.  Any value returned from the break will
be ignored, an d the computation will proceed."

2)  CLEARBUF takes two arguments in the manual and only one in the VM ????
Is this a change to the VM.

3) GETINTERRUPT[char] allows char to be only character codes, class names, T
or NIL as arguments.  If char =T returns a list of all current interrupts.  If
char=NIL returns a list of just user interrupts.  If char=<system interrupt class>
returns the charactercode which is enabled for that interrup (or NIL if none);  if
char=charactercode returns the class of interrupt for that character  code.

4)SETTINTERRUPT[char;class]
	if char is a system class name
		then disables that interrupt class, returns 
	else 
	 if class is a system class name
	  then disables the previous character for that class
	 enables char with interrupt class class