* plug-ins/gfig/README: removed some very obsolete stuff.

* plug-ins/gfig/gfig-arc.c
* plug-ins/gfig/gfig-arc.h
* plug-ins/gfig/gfig-bezier.c
* plug-ins/gfig/gfig-bezier.h
* plug-ins/gfig/gfig-circle.c
* plug-ins/gfig/gfig-circle.h
* plug-ins/gfig/gfig-dobject.c: small cleanups