[GRASS5] NVIZ and threaded TCL 8.4 working

[Cedric Shock]

A quick correction,

> ... I also found one case of sprintf-ing to interp->result without
> allocating memory and replaced it with the appropriate (Tcl_SetResult?)
> code.

grepping the code it looks like there are at least 30 more of these. They 
aren't segfaults because TCL is already prepared for them (it's even 
documented). result is initialized pointing to space for about 200 
(TCL_RESULT_SIZE) characters. I'd guess that sprintf-ing to result is much 
more future proof than sprintfing to a local variable. I'll undo that part of 
my changes.

--Cedric Shock