r3.univar: avoid compiler warnings

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@74214 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.univar/r3.univar_main.c

@@ -88,7 +88,7 @@ int main(int argc, char *argv[])
     unsigned int x, y, z;
     double dmin, dmax;
     int zone, n_zones, use_zone = 0;
-    char *mapset, *name;
+    const char *mapset, *name;
 
     struct GModule *module;