package/libgphoto2: bump version to 2.5.26

Removed md5 hash, reformatted remaining hashes.
Added optional support for libcurl available since version 2.5.24.

Release notes: https://github.com/gphoto/libgphoto2/blob/master/NEWS



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>