It now uses inline diff format for diff HTML mails

This makes the security token more robust agains session fixation
attacks. A CSRF warning will no longer abort a page save but lead to the
preview mode to avoid information loss when a user logs in during
editing (eg in another tab).

As we need to keep all core meta files anyway (the only core file that
had been deleted but shouldn't be deleted is the .indexed file) and
plugins can keep care of their own metadata files using the
IO_WIKIPAGE_WRITE event there is no reason for using the expensive
metaFiles() function during the deletion of pages.

This changes the cache logic for metadata. It introduces a new mode that
tries to avoid rendering the page again for simple requests but still
updates the metadata when the page has been changed (but not when the
cache timeout has been reached or purge is used). It simply compares the
time of the last rendering with the last modified time of the page.

The old boolean $render parameter has been changed into an int with
three possible values. Compatibility for the old parameter is provided
using a check with is_numeric using the following mapping:
- false is still don't render (0 is the new value for that)
- true is using that new render logic which means that many plugins will
  still work unchanged even if they request a lot of data using
  $render=true (1 is the new value for that providing full compatibility
  in the case 1 has been used instead of true)

The default value for p_get_first_heading is now that new simple cache
logic, the default value for getting metadata is the cache logic which
should be used with care but is the only way to request (rendered)
metadata that can change because of plugin installations or upgrades.

The value is still passed by reference as the parameter of the called
function is declared as reference.

As discussed on the mailing list [1] this patch replaces the
COMMON_PAGE_FROMTEMPLATE with a more flexible event to better intercept page
template use.

Plugin authors need to change their plugins. Details on the event are
available at [2]

[1] http://www.freelists.org/post/dokuwiki/COMMON-PAGE-FROMTEMPLATE-event
[2] http://www.dokuwiki.org/devel:event:common_pagetpl_load

This reverts commit 48714142.
Additionally there is a new fix for FS#2107 that doesn't introduce a lot
of checks but instead ensures that the configuration option can't be set
to negative values when the configuration manager is used.

As of VIM 7.3 it is no longer possible to specify the encoding in the
modeline. This gives an error message whenever such a file is opened,
thus this commit removes the enc setting from the modeline.

This fixes an infinite loop in breadcrumbs() and makes the behaviors in
all places where breadcrumbs are used consistent so that non-numeric
values, values < 0 and 0 are treated the same way.

and allow notification of subscribers of page deletion.

Often URL parameter keys contain characters which are not allowed in URIs, like square brackets. Those have to be escaped as well.

This needs testing. We need feedback from someone where this is
reproducible broken before applying this patch.