make media query list optional in syntax

Author: annevk

css3-mediaqueries/Overview.html

@@ -560,7 +560,7 @@ <h2 id=syntax><span class=secno>3. </span>Syntax</h2>
    rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
 
   <pre>media_query_list
- : S* media_query [ ',' S* media_query]*
+ : S* [media_query [ ',' S* media_query ]* ]?
  ;
 media_query
  : [ONLY | NOT]? S* media_type S* [ AND S* expression ]*
@@ -570,7 +570,7 @@ <h2 id=syntax><span class=secno>3. </span>Syntax</h2>
  : IDENT
  ;
 expression
- : '(' S* media_feature S* [':' S* expr]? ')' S*
+ : '(' S* media_feature S* [ ':' S* expr ]? ')' S*
  ;
 media_feature
  : IDENT

css3-mediaqueries/Overview.src.html

@@ -416,7 +416,7 @@ <h2>Syntax</h2>
 <code>media_list</code> production from CSS2. [[!CSS21]]</p>
 
 <pre>media_query_list
- : S* media_query [ ',' S* media_query]*
+ : S* [media_query [ ',' S* media_query ]* ]?
  ;
 media_query
  : [ONLY | NOT]? S* media_type S* [ AND S* expression ]*
@@ -426,7 +426,7 @@ <h2>Syntax</h2>
  : IDENT
  ;
 expression
- : '(' S* media_feature S* [':' S* expr]? ')' S*
+ : '(' S* media_feature S* [ ':' S* expr ]? ')' S*
  ;
 media_feature
  : IDENT