tables: adding column before a cell that's been merged to the right will create another tdspan=2 cell in new column.

[Jude Allred]

repro steps:

1. go to ​http://ckeditor.com/demo using firefox.
2. click inside the "Italian" cell of the table
3. Merge that cell to the right. We now have a "ItalianCappuccetto Rosso" cell.
4. Right click in that cell and insert a column 'before'
5. [bug] the new colomn on the left has a tdspan of 2, and the table is borked:

<table align="right" border="1" cellpadding="1" cellspacing="1" style="width: 200px;">
	<caption>
		<strong>International Names</strong></caption>
	<tbody>
		<tr>
			<td>
				&nbsp;</td>
			<td>
				Chinese</td>
			<td>
				<i>小紅帽</i></td>
		</tr>
		<tr>
			<td colspan="2">
				&nbsp;</td>
			<td colspan="2">
				Italian<i>Cappuccetto Rosso</i></td>
		</tr>
		<tr>
			<td>
				&nbsp;</td>
			<td>
				Spanish</td>
			<td>
				<i>Caperucita Roja</i></td>
		</tr>
	</tbody>
</table>

The expected output is:

<table align="right" border="1" cellpadding="1" cellspacing="1" style="width: 200px;">
	<caption>
		<strong>International Names</strong></caption>
	<tbody>
		<tr>
			<td>
				&nbsp;</td>
			<td>
				Chinese</td>
			<td>
				<i>小紅帽</i></td>
		</tr>
		<tr>
			<td>
				&nbsp;</td>
			<td colspan="2">
				Italian<i>Cappuccetto Rosso</i></td>
		</tr>
		<tr>
			<td>
				&nbsp;</td>
			<td>
				Spanish</td>
			<td>
				<i>Caperucita Roja</i></td>
		</tr>
	</tbody>
</table>

Or, in more-english-than-not, the cell created is improperly receiving the attribute 'colspan="2"'. Removing that attribute restores order to the universe.