[css-text-decor-4] Fix the treatment of % in stroke-dasharray/etc to match SVG2.

Author: tabatkins

css-text-decor-4/Overview.bs

@@ -427,7 +427,7 @@ Dashed Strokes {#stroke-dashes}
 		Initial: none
 		Applies to: inline boxes and <a>SVG shapes</a>
 		Inherited: yes
-		Percentages: relative to the <a>scaled diagonal</a> of the containing block
+		Percentages: relative to the length of the stroked path
 		Media: visual
 		Computed value: as specified
 		Animatable: as repeated list of length, percentage or calc
@@ -450,10 +450,6 @@ Dashed Strokes {#stroke-dashes}
 			If all values are zero, it is treated as ''stroke-dasharray/none''.
 	</dl>
 
-	The <dfn>scaled diagonal</dfn> of a rectangle is the length of its diagonal divided by &sqrt;2.
-
-	Issue: Percentages are stupid. Can we replace this definition with “relative to 'stroke-width'”?
-
 	Issue: SVG allows comma separation. Do we need to allow this in CSS for back-compat? (Please say no.)
 
 ### Stroke Dash Start Position: the 'stroke-dashoffset' property ### {#stroke-dashoffset}
@@ -464,7 +460,7 @@ Dashed Strokes {#stroke-dashes}
 		Initial: 0
 		Applies to: inline boxes and <a>SVG shapes</a>
 		Inherited: yes
-		Percentages: relative to the <a>scaled diagonal</a> of the containing block
+		Percentages: relative to the length of the stroked path
 		Media: visual
 		Computed value: as specified
 		Animatable: as repeated list of integers