Declare all dsfs as a dedicated type name 'DSF'.

In this commit, 'DSF' is simply a typedef for 'int', so that the new
declaration form 'DSF *' translates to the same type 'int *' that dsfs
have always had. So all we're doing here is mechanically changing type
declarations throughout the code.

auxiliary/divvy-test.c

@@ -7,7 +7,7 @@
 
 int main(int argc, char **argv)
 {
-    int *dsf;
+    DSF *dsf;
     int i;
     int w = 9, h = 4, k = 6, tries = 100;
     random_state *rs;