autorisations suffisants -> permissions suffisantes

This should avoid problems when a WiFi login redirect intercepts the
update check.
See https://forum.dokuwiki.org/post/45076

as discussed in 22db8df7

Sometime the passed AUTH was not correct. This is a quick fix,
but the whole media manager handling is one stining pile of crap that
needs a major rewrite.

Removed creation of <meta name="date" as suggested in issue #740 thread

the triggered event did not allow event handlers to change the passed
data

Restores vanished changes of #84

Sometimes users report bugs or problems releated to HTTP connections
made by our HTTPCient (eg. in the extension manager or XMLRPC).
Debugging those problems previously required modifying some sources to
enable the debugging output of the HTTPClient.
This patch adds a way to enable the debugging via a request parameter.
Since HTTP requests are often done only *after* some button was clicked,
the parameter is also looked for in the referrer of a request.
Debugging output is enabled through the existence of the parameter
'httpdebug' and is directly printed to the screen. Debugging HTTP only
works when allowdebug is enabled.

This now pulls all data from official jQuery sources. Either their CDN
or their github account. Google tends to serve outdated or even broken
files :-(

Unfortunately there's no simple way to get the latest stable jQuery-UI
so for now the version has to be adjusted manually in the script.