v4l2-sysfs-path: Rewrite it to get better results

v4l2-sysfs-path: Rewrite it to get better results

From the old v4l2-sysfs-path, we've kept just the name. The
entire old code were sent to /dev/null. On its place, a new
code were added, that reads direcly the /sys/class/<subsystem>
device links, and associates devices from video4linux, alsa
and dvb subsystems.

Also, to make easier to be used inside applications, the
discover methods were added under a LGPL library. The end
result is that v4l2-sysfs-path is now just 3 function calls.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>