Add Zen type conditional styles support

This is a basic port of the conditional styles module code as used by Zen. It allows IE conditional stylesheets to be linked in info files instead of just pasted into the head of page.tpl.php.

This patch probably needs some work yet, including some documentation, but is functional. Also attached is the conditional styles inc from zen which is required (cvs won't let me add and thus produce a patch with it included?). You need to rename it to "template.conditional-styles.inc", it's not actually a patch.

As a bonus this fixes a bug in the clean sub themes, they were including the base themes ie fix css like so:

<!--[if lt IE 8]><link type="text/css" rel="stylesheet" media="all" href="<?php print $path; ?>/css/ie-lt8.css" /><![endif]-->

Which was giving the following broken link:

<!--[if lt IE 8]><link type="text/css" rel="stylesheet" media="all" href="/sites/all/themes/clean/subthemes/clean_1kb//css/ie-lt8.css" /><![endif]-->

So with this patch all subthemes except clean_1kb now correctly inherit the base theme's IE fix stylesheet. There's an issue with clean_1kb sub theme because it has this in it's template.php:

  // Rebuild styles variable.
  $variables['styles'] = drupal_get_css(clean_css_stripped());

Which appears to wipe off the conditional css stylesheets. Need to experiment with a fix for that.

A small tweak to the patch that gets things working in clean_1kb. You'll still need a copy of template.conditional-styles.inc as above to get this patch working.

Just needs some documentation in the readme.txt I think, and it's good to go, unless anyone else has a comment...

A third patch with a little documentation in the readme. Also removes a big chunk of seemingly out of date text from the read me.

I've gone as far as I can with this. Needs review!

Final patch after code cleanup and readme text changes suggested by psynaptic.

Patch from #6 Committed along with template.conditional-styles.inc

Marking fixed.