Semantics of ^^, Version 3 (Final?)

[Don]

CHANGES BASED ON FURTHER COMMENTS
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x ^^ y is right associative, and has a precedence intermediate between
  unary and postfix operators.
The type of x ^^ y is the same as the type of x * y.

* If either x or y are floating-point, the result is pow(x, y).

If both x and y are integers, the following rules apply:

  * If x is the compile-time constant 0, x^^y is rewritten as (y==0)? 1 : 0
  * If x is the compile-time constant 1, x^^y is rewritten as (y,1)
  * If x is the compile-time constant -1 and y is an integer, x^^y is 
rewritten as (y & 1) ? -1 : 1.

  * If y == 0, x ^^ y is 1.
  * If y > 0,  x ^^ y is functionally equivalent to
     { auto u = x; foreach(i; 1..y) { u *= x; } return u; }
  * If y < 0, an integer divide error occurs, regardless of the value of x.

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Note that by definining the 0,1, -1 cases as "rewriting" rules rather 
than return values, it should be clearer that they don't apply to 
variables having those values.
I think this covers everything useful, while avoiding nasty surprises like

double y = x ^^ -1; // looks like reciprocal, but isn't!
// Yes, this IS the same problem you get with double y = 1/x.
// But that's doesn't make it acceptable. I have a possible solution to 
that one, too.

I don't think we can afford to spend much more time on this.
Is everyone happy now?