lttv: Extra arguments in runlttv

Here's an alternate take on specifying extra arguments for LTTV in the runlttv
script. They are specified on the command line after the optionnal "helper"
program name. This is more in line with the way commands like `xargs` take
extra arguments for the executable they invoke.

Signed-off-by: Benjamin Poirier <benjamin.poirier@polymtl.ca>