[css-text-4] Tweak how virtual word boundaries prohibitions are set

Set character-based virtual-word-boundary prohibitions based on UAX 14
classes rather than unicode General Caterogies.

Author: frivoal

css-text-4/Overview.bs

@@ -302,13 +302,31 @@ Detecting Word Boundaries: the 'word-boundary-detection' property</h4>
 			where words are separated by spaces or other separating characters,
 			''word-boundary-detection/auto(<lang>)'' has no effect.
 
+		<li>
+			between characters that compose a single [=typographic character unit=].
+
+		<li>
+			between a [=typographic letter unit=]
+			and a subsequent [=typographic character unit=] from the [[!UAX14]] CL, CP, IS, or EX line break classes,
+
+		<li>
+			between a [=typographic letter unit=]
+			and a preceeding [=typographic character unit=] from the [[!UAX14]] OP line break class,
+
+		<li>
+			between a [=typographic letter unit=]
+			and an adjacent [=typographic character unit=] from the [[!UAX14]] GL, WJ, or ZWJ line break classes.
+	</ul>
+
+	The User Agent should not insert a [=virtual word boundary=]:
+	<ul>
+		<li>
+			between a [=typographic letter unit=]
+			and a subsequent [=typographic character unit=] from the [[!UAX14]] PO, NS line break classes,
+
 		<li>
 			between a [=typographic letter unit=]
-			and a subsequent [=typographic character unit=] from the [[!UNICODE]] Pe or Pf classes,
-			or between a [=typographic letter unit=]
-			and a preceeding [=typographic character unit=] from the [[!UNICODE]] Ps or Pi classes,
-			or between a [=typographic letter unit=]
-			and an adjacent [=typographic character unit=] from the [[!UNICODE]] Pc or Pd or Po classes.
+			and a preceeding [=typographic character unit=] from the [[!UAX14]] PR line break class,
 	</ul>
 
 <h4 id=word-boundary-expansion>