it's seperate thread to do it's work. On my machine initial testing
seems to indicate that this works for splitting up the work between
the GUI updates (gtk+) and GEGL doing processing in the background.
No locks added thus far.
* configure.in: add GTHREAD to DEP
* gegl.pc.in: link with gthread.
* gegl/gegl-init.c: (gegl_init): call g_thread_init
* gegl/gegl-processor.c: (gegl_processor_class_init),
(gegl_processor_render), (render_thread), (gegl_processor_work): Added
an alternate code path which can be enabled by removing the comments
for the ENABLE_THREADING #define on line 486.

svn path=/trunk/; revision=1411