function mergePre( preBlock )
	{
		var previousBlock;
		if ( !( ( previousBlock = preBlock.getPreviousSourceNode( true, CKEDITOR.NODE_ELEMENT ) )
				 && previousBlock.is
				 && previousBlock.is( 'pre') ) )
			return;

		// Merge the previous <pre> block contents into the current <pre>
		// block.
		//
		// Another thing to be careful here is that currentBlock might contain
		// a '\n' at the beginning, and previousBlock might contain a '\n'
		// towards the end. These new lines are not normally displayed but they
		// become visible after merging.
		var mergedHtml = replace( previousBlock.getHtml(), /\n$/, '' ) + '\n\n' +
				replace( preBlock.getHtml(), /^\n/, '' ) ;

		// Krugle: IE normalizes innerHTML from <pre>, breaking whitespaces.
		if ( CKEDITOR.env.ie )
			preBlock.$.outerHTML = '<pre>' + mergedHtml + '</pre>';
		else
			preBlock.setHtml( mergedHtml );

		previousBlock.remove();
	}
Merge a <pre> block with a previous sibling if available.