2000-04-19  Michael Natterer  <mitch@gimp.org>

	* app/bucket_fill.c
	* app/by_color_select.c
	* app/fuzzy_select.c
	* app/preferences_dialog.c: made the "default_threshold" gimprc
	variable work as advertized:

	- initialize the thresholds with it.
	- use it for "Reset".
	- added a widget to the "Tool Options" preferences page.
	- noticed that the "Reset" button of "By Color Select" doesn't
	  behave like all the other "Reset" buttons and changed it to
	  reset the ui, not the selection.
	  (There is now a "None" button and because it was so trivial, I
	  couldn't resist to add "All" and "Invert" buttons, too)

	* libgimp/Makefile.am
	* libgimp/gimpui.c: new file.
	* libgimp/gimpui.h: new function gimp_ui_init() which will be
	called by all plugins which have a ui (not only by those with a
	preview because plugins should always follow gimp's colormap
	installation policy).

	Could someone please check if the FIXME stuff in the function
	is the right thing to do (TM). Does GdkRGB allocate the correct
	colors for the widgets in all cases or do we have to find another
	way to ensure this across processes (gtk instances)?