detect rng seed strength at runtime based on algorithm not compile time based on platform features

src/decl.c

@@ -120,6 +120,7 @@ NEARDATA boolean mrg_to_wielded = FALSE;
 /* weapon picked is merged with wielded one */
 
 NEARDATA boolean in_steed_dismounting = FALSE;
+NEARDATA boolean has_strong_rngseed = FALSE;
 
 NEARDATA coord bhitpos = DUMMY;
 NEARDATA coord doors[DOORMAX] = { DUMMY };

src/hacklib.c

@@ -899,8 +899,10 @@ init_random()
 void
 reseed_random()
 {
-    /* reseed */
-    init_random();
+   /* only reseed if we are certain that the seed generation is unguessable
+    * by the players. */
+    if (has_strong_rngseed)
+        init_random();
 }
 
 time_t