[GRASS5] Presence of NULL data in raster maps?

[Markus Neteler]

Hi,

there seems to be missing a function which reports the presence 
of NULL data in a raster map. This functions is needed for 
interfacing GRASS to GDAL, especially for 8 bit data.
At time the entire map must be scanned, right? This
can become pretty time consuming.

Is it sufficient to test the presence of the 'null' file 
within this potential function? A bit dirty, but otherwise the
cellhd file needed an addition (null: true or whatever).

Suggestions (or code)?

Markus