[css-multicol-2] Update columns definition

Adds the proposed definition for the columns property. See w3c#12050

Author: rachelandrew

css-multicol-2/Overview.bs

@@ -662,7 +662,7 @@ The multi-column model</h2>
 	See <a href="#a11y">Accessibility Considerations</a> for more details.
 
 <h2 id="the-number-and-width-of-columns">
-The number and width of columns</h2>
+The number and size of columns</h2>
 
 	Finding the number and width of columns is fundamental when laying out multi-column content.
 	These properties are used to set the number and width of columns:
@@ -943,15 +943,15 @@ The number and width of columns</h2>
 	in the multicol container and new rows of that size are created for the overflow,
 	thus honoring the 'wrap' value.
 
-<h3 id="columns">The 'column-width', 'column-count', 'column-height', and 'column-wrap' Shorthand: The 'columns' Property</h3>
+<h3 id="columns">The 'column-width', 'column-count', and 'column-height' Shorthand: The 'columns' Property</h3>
 
 	<pre class="propdef shorthand">
 	Name: columns
-	Value: <<'column-width'>> || <<'column-count'>> || <<'column-height'>> || <<'column-wrap'>>
+	Value: <<'column-width'>> || <<'column-count'>> / <<'column-height'>>?
 	</pre>
 
 	This is a shorthand property for setting 'column-width', 'column-count',
-	'column-height', and 'column-wrap'.
+	and 'column-height'.
 	Omitted values are set to their initial values.
 
 	<div class="example">
@@ -964,11 +964,12 @@ The number and width of columns</h2>
 		columns: 2 auto;    /* column-width: auto; column-count: 2 */
 		columns: auto;      /* column-width: auto; column-count: auto */
 		columns: auto auto; /* column-width: auto; column-count: auto */
-		columns: 12em 14em; /* column-width: 12em; column-height: 14em; */
-		columns: 12em 14em wrap;  /* column-width: 12em; column-height: 14em; column-wrap: wrap; */
+		columns: 12em / 14em; /* column-width: 12em; column-height: 14em; */
 		</pre>
 	</div>
 
+	Issue(12050): The syntax of the 'columns' shorthand, with the inclusion of 'column-height', is still unresolved.
+
 	<wpt>
 	multicol-columns-001.xht
 	multicol-columns-002.xht