We now have two defines for checking for UTF-8 and Unicode property
support in PREG and use them to work around FS#2636 on older systems.

we now touch the messages before the actual update happens. this should
lower the chance of more than one update check running at a time.

In the recent refactoring of the HTTPClient, a problem with certain
systems was reintroduced. On these systems a select() call always
waits for a timeout on the first call before working properly on the
second call.

This patch reintroduces the shorter timeouts with usleep rate limiting
again.

Since this bug is not reproducible on other systems it can't be unit
tested unfortunately.

Appending files now works at least for uncompressed tar files. Seeking
in compressed tars is not yet supported.

You can give a path and file contents in an array. However this didn't
work because the file_exist() check was done before checking for an
array

Internet Explorer 8 (and maybe others) seem to use different
capitalization in the ACCEPT_CHARSET header between "normal" requests
and AJAX requests. This causes a browser UID mismatch and thus an
unecessary reauthentication.

Replaced it by the old tpl_include_page() and made it more flexible by adding a boolean $propagate parameter.
(It's false by default for backwards compatibility reasons. Should it rather be true? That would probably be what most users want.)

This problem was reported in https://forum.dokuwiki.org/thread/8143.
Apart from warnings you could notice that when you have namespaces "foo"
and "f.o" and you open the sitemap for "foo" that "f.o" is opened, too.

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.

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.

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).