Detect stock N900 browser as mobile browser

Transmitted user agent looks like this:

"Mozilla/5.0 (X11; U; Linux armv7l; de-DE; rv:1.9.2.3pre) Gecko/20100723
 Firefox/3.5 Maemo Browser 1.7.4.8 RX-51 N900"

Request #12613
Signed-off-by: Michael M Slusarz <slusarz@horde.org>
Use spellchecker delimiter that is less likely to appear in spelling text (Bug #12619)