wp_register_style should default the media to 'all'

[filosofo]

What makes this a defect is that some browsers, such as Konqueror, will disregard the stylesheet if the media attribute is empty.

By default, if you register a style like so:

wp_register_style('handle', 'path/to/style.css'); 

The media is set to false, so it comes out like this:

<link rel='stylesheet' href='/path/to/style.css?vers=whatever' type='text/css' media='' />

The do_item() method of WP_Styles does set media to "all" if $media is unset. However, when it comes from wp_enqueue_style on default, the media variable is set---to false.

[westi]

(In [9404]) Default media type to all. Fixes #8000 props filosofo.