[GRASS5] G3d History support

Hi all,
i have added history support for g3d files.
If you make a cvs update, please do a make clean
and build all again, i had to change G3d.h.

r3.info will show now the history.

I also updated the g3dlib.dox file.

If i made something wrong, or the support is not proper implemented,
please mail me.

Best
Soeren