This fixes several problems:
- the CSS cache was only updated when either the CSS files for all media
  types or one of the global files was modified
- when only the screen CSS was changed, the screen CSS was regenerated
  but then the cache was printed which either caused duplicated screen
  CSS output when gzip output was disabled or invalid output with gzip
  enabled as first the plain text screen CSS and then the
  gzip-compressed cache file was printed

Now first all CSS files are collected, then the cache is checked once
and only after this the CSS content is collected.

this is a temporary and somewhat ugly fix. digest subscriptions should
make use of the inline format just as the 'every' subscriptions do.
But it makes sense to implement it correctly in the subscription branch
instead and not introduce new code in the RC.

The link doesn't exist in the English version and it doesn't work
anymore because appending a parameter to a link doesn't work when the
link is not just a URL but an HTML link

This fixes error messages about invalid plugin names for directories in
the plugin directory which didn't contain any plugin. Now the message is
only displayed for plugins which couldn't be loaded because of the
invalid name.

This simplifies a while loop in the js_compress() code. The
functionality of the new code is completely identical to the old code
but it uses less comparisons and according to FS#2593 it is thus a lot
faster.

According to the documentation the function was removed in PHP 5.4.0
though it still seems to exist in my PHP 5.4.6 installation.

This fixes the problem that media items in the feed got the title of the
previous item when useheading was enabled as no metadata is loaded for
media entries and thus the previous metadata was used again. This also
fixes dates for media files.

(How the hell did they get back in?)

The height handling code was triggered before the width handling code
and thus the right pane was below the other panes during the height
calculations which caused strange effects. Now the height handling code
is called again after adjusting the width of the right pane.

This fixes the section edit highlighting when the start marker (normally
a heading) is inside other HTML elements like a div from the wrap
plugin.

added missing info.txt parameters, added plugin plugin's info.txt, adjusted old default  template's description

The problem with using include is that when the file that is loaded
does not contain the plugin class (e.g. because the directory name is
wrong), the file could be loaded again when the plugin class is
requested a second time which will lead to a fatal error because of
class redeclaration.

This partially reverts de50cad6 as the
strict check breaks existing plugins and this shouldn't be changed
without prior discussion and a warning for plugin authors with some time
to adjust their plugins. Now all characters that are valid in PHP class
names except "_" are allowed.

This adds more tolerance to the width calculations of the media manager
panes which avoids that the right pane is displayed below the other
panes.

Before this change it was possible to send arbitrary HTML content to
subscribers, if you are using HTML subscription mails and have
untrustworthy editors, it is recommended to upgrade as soon as possible
(this doesn't affect the current stable release).

This displays an error message when building the plugin list and an
enabled plugin does not follow the plugin naming conventions. This
should help plugin developers and admins understand why their plugins
aren't working.

When loading plugins, $lang might not be initialized yet, so use a
hardcoded error message instead, especially as this error should only be
displayed for the admin (and then fixed). This also removes the
previously localized message, it might be re-added as part of the new
extension manager.

This checks if plugin names are valid and only loads valid plugin files,
this could prevent some errors from wrong upgrades as described in
FS#2464.

The BOM at the beginning of some plugin.info.txt files prevented the
plugin manager from correctly reading the base property and thus it
installed the plugin in the wrong directory.

update the url to the latest one used in the manager (FS#2463)