* plug-ins/gfig/gfig-types.h: new file to hold the types gfig uses.
  This makes the sources easier to read.

* plug-ins/gfig/Makefile.am: added gfig-types.h

* plug-ins/gfig/gfig.h: removed some types definitions and put them
  in gfig-types.h and ...

* plug-ins/gfig/gfig-dobject.h
* plug-ins/gfig/gfig-style.h: ...into these files.