give IEMGUI externals their own copy of the old functions so that the new impl of g_all_guis.c can evolve freely

suppress creation of drawcurve, drawnumber, drawsymbol and plot when the user tries to create them inside a group.  (Currently their click and motionfns don't take the parent transformation matrix into account)

big refactoring #11 : replaced %lxOBJ by x%lx and removed nlet_tag from all iemgui, among other smaller changes

big refactoring #10 : simplifying the _draw_new, _draw_select, _new, _dialog methods, among other things

*cleaned up formatting to make source more legible

fix bug about -d 4 not being applied on lines that follow a %s whose string ends in \n, such as all sys_gui

big refactoring #8 : fusion of [hsl] and [vsl] together, and fusion of [hradio] and [vradio] together

* suppress redraws for drawing commands if the group that contains them is getting deleted

remove install-icon rule from install rule, because there's already another icon & desktop file in packages/linux_make/