in search of a userdir, was: plot2d cannot create maxout.gnuplot

Vadim V. Zhytnikov writes:
>>
>> when this problem is resolved, i want to go ahead with the 5.9.2 release.
>> conversely, if this problem is not resolved, i am inclined to go ahead
>> anyway -- a lot of stuff has changed since 5.9.1 and the benefit of
>> allowing users to access the new version outweighs the lack of a
>> fix for this particular problem.
> 
> 
> I'll try to do such patch and test it on Linux,
> Windows XP and Windows Me but tomorrow.
> 
> BTW Valker's plot patch reminded me about pm3d
> gnuplot option (nice colored 3d plots).
> What about making it true by default?
> The only trouble is that it can cause
> gnuplot error with older gnuplot versions
> (< 4.0).  Alternatively we can turn it on
> on Windows where we are sure that gnuplot
> is 4.0.
> 

If nobody mind I'm going to add new variable *maxima-tempdir*.
By default it will be set to user home directory ($HOME or 
%USERPROFILE%) but as usual can be overridden by environment
variable MAXIMA_TEMPDIR.

-- 
      Vadim V. Zhytnikov