Attention: $lang['register'] has been renamed to $lang['btn_register'],
anyone using that in any plugin or template should adjust it.

This patch allows to use the placeholders in the search intro message that
will be replaced with the search term.

@SEARCH@ will be replaced with the search query
@QUERY@  will be replaced with the URL encoded search query for use in URL
         parameters

Please note that the replacement is don't on the XHTML *after* parsing and
rendering the intro wiki text. This means you can not use the query where
an ID would be expected.

Examples:

  This will work:
    [[http://www.google.com/search?q=@QUERY@|Google for @SEARCH@]].

  This will not work and will link to the page "search" instead:
    [[@SEARCH@|Your page]].

  You could use this instead:
    [[this>doku.php?id=@QUERY@|Your page]].

This reverts commit fa7c70ff.

This commit fixes two bugs that occurred when msg() was called after
html_msgarea() had already been called.
- the $MSG array is now cleared when it has been printed (otherwise $MSG
  has been printed again when another msg() call was done)
- headers_sent() didn't work for me, it always reported false although
  html_msgarea() had already been called which might be explainable with
  output buffering. This makes msg() now depend on the first call of
  html_msgarea() or headers_sent() in order to not to break msg() in
  ajax requests etc.

make custom buttons possible with html_btn() without the need of global $lang (more consistent with tpl_pagelink())

The page name lookup only checked whether the namespace part occured in the page name and dropped all other search criteria. Moreover, cleaning is not necessary anymore as ft_pageLookup does this itself.

of another term. Word boundaries are now respected.

In WebKit, newlines at the end of input field’s value parameters are removed. This breaks $PRE, so we protect those new lines with a dot and later remove the dot.

Template authors might need to adjust their CSS

This patch changes the ft_pageLookup function to always return the
title of pages with the result. This makes it easier to work with the
array, as it no longer changes between numeric and key indexes depending
on useheading.
This also means that action plugins subscribed to
SEARCH_QUERY_PAGELOOKUP need to be adjusted. The event contains a new
data field called 'has_titles' which plugins can use to check for
backwards compatibility.

When the page is not editable or the section info is out of date, a custom
editor should not be used.

The new COMMON_PAGE_FROMTEMPLATE is triggered by pageTemplate AFTER the template
has been read but before performing the template replacements.