Fix Bug when trying to send a mail after the SMTPMailSender threw an exception

Added a abort() function to cancel the current process.
In case the SMTPMailSender throws an exception which is catched by another script, no further mails could be sent because the last command was not aborted.
It may be a good idea to use a different exception type than "SystemException"
Update de.xml
Update en.xml
added 2 aliases for X( smiley

>.< and >_<
corrected 2 smileys >.< and >_<

fixed comment issue:
https://github.com/WoltLab/WCF/pull/1608#issuecomment-31148990
this:
<smiley name="&lt;X">
confused me :)
added rel="nofollow" for spiders external urls
reddit icon as .svg

for higher dpi’s, like mobile phones and retina displays.
you can set the background color to #5f99cf if you like, so it would
get the default reddic background.

i’ve created this icon, to avoid copyright issues.
added box-shadow for reddit

new preview: http://picul.de/NTe
forgot the file extension o.O
remove APC completely
Update VersionableDatabaseObjectAction.class.php
reread objects
adding MODULE_SMILEY and remove defined

adding MODULE_SMILEY and remove defined MODULE_USER_SIGNATURE
use https://secure.gravatar.com/
Added limit option
Added permission check for PHPInfoPage
add default colors for icons
rename german twitter options
rename en twitter options
Small style optimization