[css-box-3] padding applies to table cells. Fixes w3c#3039.

Author: fantasai

css-box-3/Overview.bs

@@ -397,7 +397,7 @@ Page-relative (Physical) Padding Properties: the 'padding-top', 'padding-right',
 		Name: padding-top, padding-right, padding-bottom, padding-left
 		Value: <<length-percentage>>
 		Initial: 0
-		Applies to: all elements except <a>internal table elements</a>
+		Applies to: all elements except: <a>internal table elements</a> other than table cells
 		Inherited: no
 		Percentages: refer to <a>logical width</a> of containing block
 		Computed value: a computed <<length-percentage>> value
@@ -416,7 +416,7 @@ Padding Shorthand: the 'padding' property {#padding-shorthand}
 		Name: padding
 		Value: <<'padding-top'>>{1,4}
 		Initial: 0
-		Applies to: all elements except <a>internal table elements</a>
+		Applies to: all elements except: <a>internal table elements</a> other than table cells
 		Inherited: no
 		Percentages: refer to <a>logical width</a> of containing block
 		Computed value: see individual properties