Simplifies modifying the cache via an action plugin

- includes, xhtml renderer adding 'node' class to <li> when it contains
  child list(s)

Move check after libraries are loaded, so that $conf['compression'] is not turned off in the case that gzopen doesn't exist while gzopen64 does exist, as inc/compatibility.php ought to have fixed.

by allowing longer TLDs (up to 63 characters, which is the DN maximum: https://tools.ietf.org/html/rfc1034):
"Each node has a label, which is zero to 63 octets in length."

For an up-to-date-length, see http://stackoverflow.com/a/22038535

that's the version in Debian old stable

this ensures there will be never, ever an outdated update message shown
after upgrade.

The existing logic for messages.txt requires some valid update
response (ending in %) to the messages update check before it clears
the current messages.

However update.dokuwiki.org appears to return an empty string response
if everything is up to date. (ie http://update.dokuwiki.org/check/46.1 )

As a result if there are update messages in messages.txt they don't
automatically go away after updating to the current version. The only
time they change is when a newer release comes out. The upgrade plugin
has logic in it to force a re-download of messages.txt, but currently
this just re-downloads the old update messages.

This change explicitly allows for "" as a valid "no messages"
indicator (distinct from false, which is the HTTP error indicator.)

Since Chrome 37, they send differen accept encodings for POST and GET
requests which will break BrowserUID checks as reported in
cosmocode/dokuwiki-plugin-oauth/issues/3

See https://code.google.com/p/chromium/issues/detail?id=410559 for
official bug report at Google

Update to latest Incutio XML-RPC Library
include also some Wordpress improvements
(see for more details the log of the lib as included in WP:
https://core.trac.wordpress.org/log/trunk/src/wp-includes/class-IXR.php )

many PHPDocs
some unused variables
some dynamically declared variables declared

remove config option