[GRASS5] usability tweak on OSX

[Hamish]

> > > > +    eval exec -- xterm -geometry -50-40 -e [...]
..
> > > We definitely shouldn't be hardcoding xterm placement inside d.m.
..
> Bad practice. Specifying -geometry will override most of the
> mechanisms by which the user can configure the placement.
..
> In general, per process settings (e.g. a -geometry switch) are
> supposed to override any "global" settings (e.g. WM configuration
> files).

Right. Command line params should always override defaults. Got it.

Is it possible for us to set xrdb/.Xresources settings on the fly?

e.g. we provide e.g. $GISBASE/etc/grass.Xresources and point xrdb to it
in Init.sh. Then (re)run xrdb on ~/.Xresources if it exists to let 
folks maintain their own preferences. (Hopefully that overrides previous
settings of the same name?)

:/


Hamish