[css-syntax] Restrict the label bytes to 7-bit ASCII.

--HG--
extra : rebase_source : 87ab91b93f7f73469004c1c347e08ff664ad2f76

Author: tabatkins

css-syntax/Overview.html

@@ -450,7 +450,8 @@ <h3 class="heading settled heading" data-level=3.2 id=input-byte-stream><span cl
 			If the first 1024 bytes of the stream begin with the hex sequence
 
 <pre>40 63 68 61 72 73 65 74 20 22 XX* 22 3B</pre>
-<p>			where each <code>XX</code> byte is anything except 22<sub>16</sub>,
+<p>			where each <code>XX</code> byte is a value between 0<sub>16</sub> and 21<sub>16</sub> inclusive
+			or a value between 23<sub>16</sub> and 7F<sub>16</sub> inclusive,
 			then <a data-link-type=dfn href=#get-an-encoding title="get an encoding">get an encoding</a>
 			for the sequence of <code>XX</code> bytes,
 			interpreted as <code>ASCII</code>.

css-syntax/Overview.src.html

@@ -288,7 +288,8 @@ <h3 id="input-byte-stream">
 
 			<pre>40 63 68 61 72 73 65 74 20 22 XX* 22 3B</pre>
 
-			where each <code>XX</code> byte is anything except 22<sub>16</sub>,
+			where each <code>XX</code> byte is a value between 0<sub>16</sub> and 21<sub>16</sub> inclusive
+			or a value between 23<sub>16</sub> and 7F<sub>16</sub> inclusive,
 			then <a>get an encoding</a>
 			for the sequence of <code>XX</code> bytes,
 			interpreted as <code>ASCII</code>.