The Windows RNG turns out to only give about 16 bits at a time. This

is (a) pretty feeble, and (b) means that although Net seeds transfer
between platforms and still generate the same game, there's a
suspicious discrepancy in the typical seed _generated_ by each
platform.
I have a better RNG kicking around in this code base already, so
I'll just use it. Each midend has its own random_state, which it
passes to new_game_seed() as required. A handy consequence of this
is that initial seed data is now passed to midend_new(), which means
that new platform implementors are unlikely to forget to seed the
RNG because failure to do so causes a compile error!

[originally from svn r4187]

net.c

@@ -254,7 +254,7 @@ char *validate_params(game_params *params)
  * Randomly select a new game seed.
  */
 
-char *new_game_seed(game_params *params)
+char *new_game_seed(game_params *params, random_state *rs)
 {
     /*
      * The full description of a Net game is far too large to
@@ -268,7 +268,7 @@ char *new_game_seed(game_params *params)
      * understand it and do something completely different.)
      */
     char buf[40];
-    sprintf(buf, "%d", rand());
+    sprintf(buf, "%lu", random_bits(rs, 32));
     return dupstr(buf);
 }