MSIE 11 tries hard to break any previous working browser detection
even through feature checks. This resolves to browser sniffing (MSIE for
old IE, Trident for IE11+)

See https://forum.dokuwiki.org/thread/10824

The regex wasn't properly escaped here which lead to problems when the
path contains backslashes. This is the root cause of the bug reported
at https://github.com/cosmocode/edittable/issues/19

fix bug that only allows admins any AJAX calls

In most cases this change will have no effect, but noes the response will use the filename that was originally requested. The downloaded filename can be modified to something different as well. E.g. the siteexport plugin will make use of it.

our translation interface used to submit empty files for a while but no
longer does, so these can go

The filename found in the URL will be used for old plugins missing a
base entry in their plugin.info.txt and lacking a subdirectory inside
the archive as well. This patch makes sure possible query strings aren't
included in the filename.

Note: io_download() will also try to get a filename from any
content-disposition header.

If no filename can be found we simply use an md5 sum of the URL and hope
the plugin will contain it's own hint for naming.

PHP_EOL is platform dependent, so you get in trouble while migrating
between platforms.

they were just catching and rethrowing

This reads some duplication in the from of haveing a Doku_Parser_Mode
and Doku_Parser_Mode_Plugin class which are basically the same but only
the latter extends DokuWiki_Plugin. This avoids the performance/RAM
problems mentioned in my previous commit. An interface keeps both
logically together.

With PHP 5.4 further deduplication could be done via Traits.

This makes Doku_Parser_Mode inherit from DokuWiki_Plugin which allows
for the removal of a bunch of duplicate code form
DokuWiki_Syntax_Plugin. This makes the code easier to maintain and makes
sure all DokuWiki plugins are actual instances of DokuWiki_Plugin.

However this adds a bunch of functions to the "normal" parser modes that
don't need them which could have performance/RAM implications.

this is not a extension specific cache but a global one. no need to
purge for each installed extension