Update slideshow-shortcode.css

Examinating the style sheet file slideshow-shortcode.css I noticed 2 errors:

line 57 .slideshow-line-height-hack {
overflow:hide;
...
}

the correct value for overflow property is "hidden".

line 102 body div div.slideshow-controls a:hover {
....
*display: inline;
....
}

Removing character * put property "display" between /* and */