YAAO (yet another assignment operator)

[Benjamin Thompson]

A bit of history :
Dean Rubine suggested a "->=" operator, to which the response has been mostly
negative. Ron at brl-tgr mentioned a more general "operator" (<binop>=).


The idea of <binop>= strikes me as a very good and very easy to implement idea.
Consider that 
		X <binop>= Y;		(call this form 1)
is exactly the same statement as
		X = X <binop> Y;	(call this form 2)

Given that <binop> is a legal operator, all C compilers already have code
to compile form 2.  All we have to do now is modify the compiler(s) to convert
form 1 to form 2.  This should be utterly trivial, and allows us to add a
nice bit of generality to C.