This allows the developer to set which header to send to the webserver. The default is X-Sendfile.
Add ability to change which header gets set when using USE_X_SENDFILE
Remove commented line
Doesn't lighttpd understand x-sendfile, too?! Because if it does there's not much value in this. The only other webserver that does things differently is nginx - but nginx uses a different thing altogether (URL instead of filesystem path) so just renaming the header won't help.
Only in 1.5 does Lighttpd understand X-Sendfile. The last stable version is 1.4. (Admittedly, 1.5 has been in RC status since at least 2007...)
I understand that this is limited in its usefulness, but it doesn't add much to the code (2 lines overall without docs) and it does increase somewhat the flexibility of the system itself.
This is better fixed with a WSGI middleware. That's what they are for :)