More portability fixes. Changed GP_UDEV to only enable UDEV support if libusb is available.
More portability fixes.
Changed GP_UDEV to only enable UDEV support if libusb is available.


git-svn-id: 84309296e5159d32aabeca12da51dba852c01f50@12349 67ed7778-7388-44ab-90cf-0a291f65f57c

gphoto/libgphoto2-sharp,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2-sharp,gphoto/libgphoto2-python