[css3-syntax] Make \0 return U+fffd as well.

Author: tabatkins

css3-syntax/Overview.html

@@ -2563,10 +2563,10 @@ <h4 id=consume-an-escaped-character><span class=secno>3.4.27. </span> <dfn
     href="#next-input-character"><i>next input character</i></a> is <a
     href="#whitespace"><i>whitespace</i></a>, consume it as well. Interpret
     the <a href="#hex-digit"><i>hex digits</i></a> as a hexadecimal number.
-    If this number is greater than the <a
+    If this number is zero, or is greater than the <a
     href="#maximum-allowed-codepoint"><i>maximum allowed codepoint</i></a>,
-    return U+FFFD REPLACEMENT CHARACTER. Otherwise, return the character with
-    that codepoint.
+    return U+FFFD REPLACEMENT CHARACTER (�). Otherwise, return the
+    character with that codepoint.
 
    <dt>anything else
 

css3-syntax/Overview.src.html

@@ -2071,9 +2071,9 @@ <h4>
 			<i>whitespace</i>,
 			consume it as well.
 			Interpret the <i>hex digits</i> as a hexadecimal number.
-			If this number is greater than 
-			the <i>maximum allowed codepoint</i>,
-			return U+FFFD REPLACEMENT CHARACTER.
+			If this number is zero,
+			or is greater than the <i>maximum allowed codepoint</i>,
+			return U+FFFD REPLACEMENT CHARACTER (�).
 			Otherwise, return the character with that codepoint.
 
 		<dt>anything else