xgdisplay bug fix.

[ray at zoro.cts.com]

I have found a bug and a fix for modify color mode in
xgdisplay when you are changing colors assigned to categories
and then try to save the modified color, the color file 
is wiped out. The problem is in:
grass/src/xgrass/display/crtecolor.c line:214

  G_write_colors(Gobj->Obj.GeoFrame.rname, Gobj->Obj.GeoFrame.rmapset,
                 Gobj->Obj.GeoFrame.colors);
}

it should be:

  G_write_colors(Gobj->Obj.GeoFrame.rname, Gobj->Obj.GeoFrame.rmapset,
                 &(Gobj->Obj.GeoFrame.colors));
}

i.e. The address of Gobj->Obj.GeoFrame.colors.

Enjoy.

<ray>