[GRASS5] d.graph updates

[Hamish]

> How easy/hard would it be to add different line widths at some point?

Easy & done.

Also added a -m flag to use geographic coordinates (the d.mapgraph merge).


TODO:  (preferably by someone else)

a) merge in G_malloc() fixes from d.mapgraph, any other bug fixes?
 After this is done we can add a
   G_warning("Module superseded; use 'd.graph -m' instead");
 to d.mapgraph. Perhaps it is preferable to remove d.mapgraph from CVS
 and have init scripts set up `alias d.mapgraph='d.graph -m'` ?

b) update "icon" instruction to use GRASS 6 symbols. This requires
 copying out the icon display code from d.vect and making a new display
 lib routine. After that we would modify d.graph to use the new
 D_symbol() fn.

-- do we want to call them symbols or icons? I find it confusing to use both.


Please read the updated help page. Pointed out a previously undocumented
feature (polyline) among other things.

It may be useful to run at DEBUG level = 3.

I think the module is pretty useful now. It will be even beter when the 
icons are updated.


enjoy,
Hamish