added dfc PKGBUILD from AUR

Hi guys,

I added dfc PKGBUILD from AUR (which is a PKGBUILD I maintain since I am the author of the software).
dfc is a command line utility tool I wrote last year and maintain now. It is a CLI too which provides disk usage information with graph and colors and has the possibility to export the information to various format such as HTML. It is written in C and has no special dependencies. If you want more information about what dfc is, I suggest you visit the wiki: http://projects.gw-computing.net/projects/dfc/wiki and eventually have a look at the FAQ: http://projects.gw-computing.net/projects/dfc/wiki/FAQ .

I compiled it without any problems directly on my Raspberry Pi. I think it would be a nice addition to your aur repository as I find this tool quite useful.

Cheers and thanks for all your hard work!