add range method

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@43575 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.neighbors/main.c

@@ -50,6 +50,7 @@ static struct menu menu[] = {
     {c_mode, w_mode, NO_CATS, 1, 0, "mode", "most frequently occuring value"},
     {c_min, NULL, NO_CATS, 1, 0, "minimum", "lowest value"},
     {c_max, NULL, NO_CATS, 1, 0, "maximum", "highest value"},
+    {c_range, NULL, NO_CATS, 1, 0, "range", "range value"},
     {c_stddev, w_stddev, NO_CATS, 0, 1, "stddev", "standard deviation"},
     {c_sum, w_sum, NO_CATS, 1, 0, "sum", "sum of values"},
     {c_var, w_var, NO_CATS, 0, 1, "variance", "statistical variance"},

raster/r.neighbors/r.neighbors.html

@@ -131,6 +131,10 @@ when these are ranged in numerical order.
    |----|----|----|          |----|----|----|
 </pre>
 
+<dt><b>range</b>
+
+<dd>The range value within the neighborhood.
+
 <dt><b>stddev</b> 
 
 <dd>The statistical standard deviation of values