This changes the previously static lastsecid into an instance variable,
this leads to consistent section edit ids when the xhtml renderer is
used more than once in a request. This makes it possible for test cases
to know the exact section edit id for an instruction array.

ACL checking of DokuWiki is currently always case-sensitive
regardless of auth backend setting ($auth->isCaseSensitive).
This commit enables case-insensitive match in the same way
of auth_isMember().

Empty BCC/CC headers may cause errors on IIS.

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.

The library now creates either a POSIX ustar prefix or a GNU longlink
entry for files which have a name longer than 100 bytes

Supports POSIX ustar prefixes and GNU longlink entries

This new class is only losely based on our previous library. The
whole API was changed to make it more flexible and memory saving.

Some fisrt unit tests are included

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