[css-values-4] Handle the rest of the pow() special-cases.

Author: tabatkins

css-values-4/Overview.bs

@@ -2706,7 +2706,20 @@ Exponential  Functions: ''pow()'', ''sqrt()'', ''hypot()''</h3>
 <h4 id="exponent-infinities">
 Argument Ranges</h4>
 
-	In ''pow(A, B)'':
+	In ''pow(A, B)'',
+	if A is negative,
+	B must be an integer,
+	or else the result is NaN.
+
+	If A and B are both 0,
+	the result is 1.
+	If A is 0⁺ and B is negative,
+	the result is +∞;
+	if A is 0⁻ and B is negative,
+	the result is -∞.
+
+	If A or B is infinite,
+	the following tables give the results:
 
 	<table class=data>
 		<thead>