[css-text-4] Clarify behavior of omitted values. w3c#5382

See w3c#5382 (comment)

Author: fantasai

css-text-4/Overview.bs

@@ -1809,6 +1809,9 @@ White Space and Wrapping: the 'white-space' property</h2>
 	Note: This shorthand combines both inheritable and non-inheritable properties.
 	If this is a problem, please inform the CSSWG.
 
+	Unless otherwise specified, any omitted [=longhand=]
+	is set to its [=initial value=].
+
 	The following table gives the normative mapping
 	of the values of the [=shorthand=]’s special keywords
 	to their equivalent [=longhand=] values.
@@ -1847,7 +1850,7 @@ White Space and Wrapping: the 'white-space' property</h2>
 		</tbody>
 	</table>
 
-	Values have the following informative definitions:
+	These keywords have the following informative definitions:
 
 	ISSUE: Remove these definitions once the tests annotations have been redistributed.