Fix SF bug #227748.

Fix SF bug #227748.

When using the flat-file back end, page names with slashes in them didn't work.
We fix this by urlencoding '%' '/' '\\' and ':' when they occur in page names.

WARNING: If any pages currently in your flat-file database contain any of
those characters in their titles, this change will make them invisible
to PhpWiki.  You should back them up before upgrading, and restore them
after upgrading.

git-svn-id: svn://svn.code.sf.net/p/phpwiki/code/branches/release-1_2-branch@542 96ab9672-09ca-45d6-a79d-3d69d39ca109