Applied patch from Jan Heller.

Applied patch from Jan Heller.
* babl/babl-fish-path.c: (get_conversion_path), (babl_fish_path),
(test_create), (init_path_instrumentation),
(destroy_path_instrumentation), (get_path_instrumentation): Improved
fish path instrumentation during the search for a new one to optimize
for speed. Added logic to disallow creation of a fish path that is
actually slower than appropriate reference fish.
* babl/babl-util.[ch]: (babl_process_cost): New function for unified
timing formula for babl processings.
* babl/babl-conversion.c: (babl_conversion_error): Make use of the
new babl_process_cost function.
* extensions/gimp-8bit.c: Added a function declaration to prevent
compiler warning.

svn path=/trunk/; revision=305