In 09edb711 most of the old userstyles were wrongly named. This renames them back to what they were before that change. See also http://www.dokuwiki.org/devel:css#user_styles

* code cleanup in lib/exe/css.php
* renamed 'default' userstyle to 'screen' in config_cascade
* splitted core lib/styles/style.css up into all.css, print.css and screen.css

Conflicts:
	inc/lang/bg/lang.php

Attention: $lang['register'] has been renamed to $lang['btn_register'],
anyone using that in any plugin or template should adjust it.

Passed every png file through http://www.smushit.com/ysmush.it/ saving some 1-2kb of binary image data

Icon downloaded from http://forum.skype.com/style_emoticons/skype/skype.png

I asked someone internally for file copyright and answer was ok (do
whatever you want)

A page could have possibly hundreds of backlinks, when the cache is
outdated they should not be rererendered at once

Quoted-Printable specifies a maximum line length and some mail tools
(Apple mail and Thunderbird) take this quite serious and will fail to
decode subjects encoded with quoted-printable when the subject exceeds
the length limit.

The correct fix would be to wrap the header into multiple lines. But
this seems not to be possible with mails() $subject variable.

This patch switches to Base64 encoding for long subjects.

A general decision if switching completely to Base64 is the best way
to go is still open. (see bugreport)