Fixes bug described in mootools#1346

Sources out the creation of the sort-span tag in order to re-inject them
on re-enable sorting.

Source/Interface/HtmlTable.Sort.js

@@ -13,6 +13,7 @@ authors:
   - Harald Kirschner
   - Aaron Newton
   - Jacob Thornton
+  - Henning Bopp <henning.bopp@gmail.com>
 
 requires:
   - Core/Hash
@@ -95,8 +96,7 @@ HtmlTable = Class.refactor(HtmlTable, {
 		if (cell.hasClass(this.options.classNoSort) || cell.retrieve('htmltable-parser')) return cell.retrieve('htmltable-parser');
 		var thDiv = new Element('div');
 		thDiv.adopt(cell.childNodes).inject(cell);
-		var sortSpan = new Element('span', {'class': this.options.classSortSpan}).inject(thDiv, 'top');
-		this.sortSpans.push(sortSpan);
+        this.getHeadSpan().inject(thDiv, 'top');
 		var parser = this.options.parsers[index],
 			rows = this.body.rows,
 			cancel;
@@ -262,6 +262,7 @@ HtmlTable = Class.refactor(HtmlTable, {
 		this.element.addClass(this.options.classSortable);
 		this.attachSorts(true);
 		this.setParsers();
+        this.head && this.head.getElements(this.options.thSelector).flatten().map(this.injectHeadSpan, this);
 		this.sortable = true;
 		return this;
 	},
@@ -275,8 +276,17 @@ HtmlTable = Class.refactor(HtmlTable, {
 		this.sortSpans.empty();
 		this.sortable = false;
 		return this;
-	}
+	},
 
+    getHeadSpan: function(parent){
+        var sortSpan = new Element('span', {'class': this.options.classSortSpan});
+		this.sortSpans.push(sortSpan);
+        return sortSpan;
+    },
+
+    injectHeadSpan: function(parent){
+        return this.getHeadSpan().inject(parent);
+    }
 });
 
 HtmlTable.ParserPriority = ['date', 'input-checked', 'input-value', 'float', 'number'];
@@ -358,4 +368,3 @@ HtmlTable.defineParsers = function(parsers){
 };
 
 })();
-