Switch toggle to semicolon-separated. Fix grammar for semicolons in mix(). w3c#6704

Author: tabatkins

css-values-4/Overview.bs

@@ -465,6 +465,16 @@ Combining Values: Interpolation, Addition, and Accumulation</h2>
 	If a value type does not define a specific procedure for <a>accumulation</a>,
 	its <a>accumulation</a> operation is identical to <a>addition</a>.
 
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+
 <h3 id="interpolate">
 Representing Interpolated Values: the ''mix()'' notation</h3>
 
@@ -473,7 +483,7 @@ Representing Interpolated Values: the ''mix()'' notation</h3>
 	whose syntax is defined as follows:
 
 	<pre class="prod">
-		mix( <<percentage>> ; <<start-value>> ; <<end-value>> )
+		mix( <<percentage>> ';' <<start-value>> ';' <<end-value>> )
 	</pre>
 
 	<dl dfn-for="mix()">
@@ -2647,18 +2657,21 @@ Toggling Between Values: ''toggle()''</h3>
 
 	The syntax of the ''toggle()'' expression is:
 
-	<pre>toggle( <<toggle-value>># )</pre>
+	<pre>toggle( <<toggle-value>> [ ';' <<toggle-value>> ]+ )</pre>
 
 	where <dfn>&lt;toggle-value></dfn> is any CSS value
-	that is valid where the expression is placed,
-	and that doesn't contain any top-level commas.
+	that is valid where the expression is placed.
 	If any of the values inside are not valid,
 	then the entire ''toggle()'' expression is invalid.
 	The ''toggle()'' expression may be used as the value of any property,
 	but must be the only component in that property's value.
 
-	The ''toggle()'' notation is not allowed to be nested; nor may it
-	contain ''attr()'' or ''calc()'' notations.
+	Note: This [=functional notation=] uses semicolons to separate arguments
+	rather than the more typical comma
+	because the values themselves can contain commas.
+
+	The ''toggle()'' notation is not allowed to be nested;
+	nor may it contain ''attr()'' or ''calc()'' notations.
 	Declarations containing such constructs are invalid.
 
 	<div class="example">