try to increase the PCRE backtrack limit

This should avoid problems with larger pages on newer PHP versions.
See http://www.freelists.org/archives/dokuwiki/04-2008/msg00049.html

darcs-hash:20080409181615-7ad00-de4f7a0602692b28e048d215c2e2b9657f96b81c.gz

inc/init.php

@@ -90,6 +90,9 @@
   // make sure global zlib does not interfere FS#1132
   @ini_set('zlib.output_compression', 'off');
 
+  // increase PCRE backtrack limit
+  @ini_set('pcre.backtrack_limit', '20971520');
+
   // enable gzip compression
   if ($conf['gzip_output'] &&
       !defined('DOKU_DISABLE_GZIP_OUTPUT') &&