Log Message:
Changes 2.3.1:
  * Added --hook-script option, including man page update and test-hook.sh.
  * Fix: --get-all-metadata takes no argument.

Changes 2.3.0:
  * Require popt library to parse command line options.
  * Partitioned command line options into groups of related options.
  * Added --debug-logfile=FILENAME option.
  * Only load all camlibs if necessary.
  * (Half-)Fix to make --with-libgphoto2=PREFIX configure parameter work.
  * Preliminary support for lower-case filenames in --filename pattern: %:
  * Added "rmdir" command to gphoto2 --shell.