Fix #16009
Merge pull request #86 from Kirill/issue16009

Fixes #16009: Bug note not showing
Fix #16010 change variable
Merge pull request #87 from Kirill/issue16010

Fixes #16010: remove usage of undeclared variable.
Fix #13304: Error handler causes XML Parsing Errors

The standard error handler was generating invalid HTML, due to not
outputting previously issued page headers.

To fix this issue, we retrieve the output buffer's contents, and retain
all html up to the </head> tag (not included).

A few layout changes were applied as well, to make better use of
screen real estate so that the error page is easier to read, especially
when $g_show_detailed_errors is ON.
Revert "Issue #12545: Enforce XHTML strict output for all pages served"

This reverts commit 4fc1d8b8290872e660c6d9a179c4c2209adf7e26.

Fixes #13304, #14759, #15446

Conflicts:

	core/http_api.php
Fix #16025: Change DOCTYPE to HTML5

As discussed in mailing list [1]

[1] http://article.gmane.org/gmane.comp.bug-tracking.mantis.devel/4468
Admin check (PHP): ignore disabled pcntl_* functions

As per PHP documentation, Process Control functions should be disabled
within a web server environment, and therefore should not pop up as
warnings.

Fixes #16035
Admin checks (Paths): remove 'scripts' from developers dirs

This directory is not for development use, it contains server back-end
scripts, e.g. to send e-mails via cron.

Fixes #16035