* app/paint_core.[ch]: set the fg or bg color if ctrl or alt is
 	held.  use the new dropper cursor.

	* app/cursorutil.[ch], app/gdisplay.[ch], app/rect_select.c: Use
 	GimpCursorType enum values > GDK_CURSOR_LAST instead of seperate
 	functions to choose between cursor types.

	* app/color_picker.c: use the new dropper cursor.

	* app/paintbrush.c, app/airbrush.c, app/paintbrush.c: use the new
 	color picking feature of paint_core.

	* cursors/dropper, cursors/droppermsk: new cursor for the color
 	picker tool. (this cursor is REALLY ugly, someone should fix it)