Add some more file extension -> lexer mappings

Mimetype detection doesn't always properly detect code (I saw javascript as
plain text, c as asm) and if there is an extension we can likely get
better result by using that.

Signed-off-by: Florian Pritz <bluewind@xinu.at>
Implement rangeDownload() as driver and provide sendfile implementations for Nginx and Lighttpd

* The rangeDownload() function has been moved to libraries/Ddownload/drivers/Ddownload_php.php
* The nginx and lighttpd drivers can be set via $config['download_driver']

Signed-off-by: Pierre Schmitz <pierre@archlinux.de>
Remove unneeded return statements after show_error

show_error() already exits after displaying the message.

Signed-off-by: Florian Pritz <bluewind@xinu.at>