Replaced integer checks that used preg_match() to use ctype_digit() instead

Added (very basic) spam filtering plugin support. Plugins can mark a message as spam by hooking into the spam check API, which is documented in functions.php. No spam checking functionality is built-in.

Login: reauth: window.location.hash is now updated to include the new SID so that page reloads will use it

AJAX core library: possible breaking change, readystatechange functions are now called with the XHR instance as the first parameter, to allow requests to run in parallel. This means much better stability but may break some applets (compatibility hack is included)

Oxygen: synced mint style

PageProcessor: fix not setting page_exists to true after create_page() success (todo: move to Namespace_*?); add $visible parameter to create_page()

Change config.new.php and .htaccess.new to have a single newline according to Fedora project guidelines

Installer: add RewriteBase to .htaccess to work properly under aliased Apache setups (generated 404s in QA)