[GRASS5] d.info: flag added for approximate screen scale

[Markus Neteler]

Hi,

I have added a new flag to d.info to print the
approximate map scale in GRASS monitor. I know that
it's not very precise, but an approximate figure
is better than nothing:

Example:

 d.info -s
 Approximate map scale in GRASS monitor <x0> 1:11000

I remember that this was removed in GRASS 5 (not by me)
but IMHO a GIS should be able to give such information.

The algorithm takes the monitor size, the map size within
the monitor and the screen resolution (x DPI and y DPI)
into account. The latter may not be precise, depending on
the X server software, video card or monitor. The 
figure is therefore given rounded.

It still needs to be make optional in the Makefile
in case of X absences. Hints for a test are welcome.

I hope the flag survives this time :-)

Markus