libgphoto2: new package

libgphoto2: new package

Add support for libgphoto2 core library designed to allow access to
digital camera.

Signed-off-by: Kevin JOLY <kevin.joly@sensefly.com>
Cc: Romain Naour <romain.naour@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Romain Naour <romain.naour@gmail.com>
[Thomas:
 - Use downloads.sourceforge.net
 - Remove final dot at end of <pkg>_LICENSE variable
 - Minor tweaks in comments.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>