Added syslinux package to install-deps
Added syslinux package to install-deps

The syslinux package is required for the 'isohybrid' invocation used in
make-master.

This package is not installed by default, as found with a fresh
14.04.2 installation.

jmcorgan/ubuntu-remaster,jynik/gnuradio-livesdr,gnuradio/gnuradio-livesdr,jynik/gnuradio-livesdr