Corrected function documentation

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@53153 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/raster/cats.c

@@ -157,7 +157,10 @@ int Rast_read_vector_cats(const char *name,
 }
 
 /*!
-   \brief Get number of categories
+   \brief Get the max category number
+
+   Return the max category number of a raster map
+   of type CELL.
 
    \param name raster map name
    \param mapset mapset name