Gphoto2

1/ Camera.get_storageinfo and Camera.capture_preview now allocate their
return value (API change).
2/ Examples include a "focus assist" program for EOS 350d. Will need changes
to work with other cameras.

1/ API change! The get_data_and_size functions now return a new "FileData"
object which has the Python buffer interface.
2/ Added get/set capture target examples.

1/ Can now use gp_camera_file_read to fetch data from camera in chunks.

1/ Bump major version number
2/ Upgrade status from "beta" to "production/stable"

1/ Ignore gp_log_with_source_location as it's not present in all versions of
libgphoto2.
2/ Minor improvements in build process.

1/ Ignore gp_log_data for compatibility with gphoto2 v2.5.6.
2/ Improved robustness of interface compilation.
3/ Made use_python_logging() configurable to control verbosity.