gcc 4.7.1 requires libv4lconvert

Hi. 

I tried to compile svv with gcc 4.7.1 and it explicitly required linking in libv4lconvert. I added it to autotools and now it seems to build ok. 

I see you're not working on svv atm, but it looked interesting and I had to check it out. Haven't yet tested it because i misplaced my webcam somewhere in the "unkown universies", but at least it builds without problems now. I will do a quick test as soon as I find my webcam.