$_SERVER['PATH_INFO'] is used now to determine the page id when using
internal rewriting, in all testcases I've seen so far this variable
was set correctly. There are also a couple of fallbacks if the variable
doesn't exist, $_SERVER['SCRIPT_NAME'] is now preferred instead of
custom path extraction which fails when doku.php is outside the document
root.

This reverts commit 7873e757.

The patch breaks at least the behaviour of the "view recent
changes of the whole wiki" link.

partly reverts previous patches to keep matching styles with other
DokuWiki buttons