[css-conditional-5] Use the generic <boolean-expr>

Author: cdoublev

css-conditional-5/Overview.bs

@@ -161,28 +161,11 @@ Generalized Conditional Rules: the ''@when'' rule</h2>
 	It is defined as:
 
 	<pre class=prod>
-		@when <<boolean-condition>> {
+		@when <<boolean-expr[ <<if-test>> ]>> {
 		  <<rule-list>>
 		}
 	</pre>
 
-	Where <dfn><<boolean-condition>></dfn> is a boolean algebra a la [[mediaqueries-4#mq-syntax]],
-	but with ''media()'' and ''supports()'' functions as leaves.
-
-	Issue: Define "boolean algebra, with X as leaves" in a generic way in Conditional,
-	so all the conditional rules can reference it directly,
-	rather than having to redefine boolean algebra on their own.
-
-	The ''media()'' and ''supports()'' functions are defined as:
-
-	<pre class=prod>
-	<dfn>media()</dfn> = media( [ <<mf-plain>> | <<mf-boolean>> | <<mf-range>> ] )
-	<dfn>supports()</dfn> = supports( <<declaration>> )
-	</pre>
-
-	A ''media()'' or ''supports()'' function is associated the boolean result
-	that its contained condition is associated with.
-
 <h2 id="else-rule">
 Chained Conditionals: the ''@else'' rule</h2>
 
@@ -209,13 +192,13 @@ Chained Conditionals: the ''@else'' rule</h2>
 	It is defined as:
 
 	<pre class=prod>
-		@else <<boolean-condition>>? {
+		@else <<boolean-expr[ <if-test> ]>>? {
 			<<rule-list>>
 		}
 	</pre>
 
 	''@else'' is interpreted identically to ''@when''.
-	If its <<boolean-condition>> is omitted,
+	If its <<boolean-expr>> is omitted,
 	it's treated as having a condition that's always true.
 
 	A <dfn export>conditional rule chain</dfn> is