2003-01-02  Michael Natterer  <mitch@gimp.org>

	Replaced Garry's fix for bug #98843 by a more general solution
	which stops the active tool when an undo group start is pushed:

	* app/core/gimpimage.[ch]: removed the "layer_merge" signal
	and added "undo_start" instead.

	* app/undo.c: emit "undo_start" in undo_push_group_start()
	_before_ checking if gimage->undo_on is TRUE.

	* app/tools/tool_manager.c: connect to "undo_start" and HALT the
	active tool if neccessary.

	* app/core/core-types.h: added EDIT_COPY_UNDO_GROUP.

	* app/core/gimpedit.c: push an undo group around the copy
	operation. Will probably have to add more undo group types to wrap
	other critical image modifications with.

	* app/core/gimpimage-merge.c
	* app/gui/convert-dialog.c
	* app/gui/edit-commands.c
	* app/gui/test-commands.c
	* app/tools/gimpimagemaptool.c: removed all special code to
	stop the active tool.