Use more portable random seed generation.

The new function md_random_seed() has replaced time() + getpid() and
similar methods.  Putting everything in mdport.c slightly reduces the
warnings and workarounds.

xrogue/main.c

@@ -166,7 +166,7 @@ main(int argc, char *argv[], char *envp[])
         seed = atoi(getenv("SEED")); 
     }
     else {
-        seed = (int) time(&now) + getpid();
+        seed = md_random_seed();
     }
     if (wizard)
         printf("Hello %s, welcome to dungeon #%d\n", whoami, seed);

xrogue/rogue.h

@@ -1505,6 +1505,7 @@ int     md_getuid(void);
 long    md_memused(void);
 int     md_normaluser(void);
 int     md_rand(int range);
+unsigned int md_random_seed(void);
 void    md_setup(void);
 int     md_shellescape(void);
 int     md_srand(int seed);

xrogue/state.c

@@ -3619,3 +3619,16 @@ md_unlink(char *file)
     return(unlink(file));
 #endif
 }
+
+unsigned int
+md_random_seed(void)
+{
+    unsigned int seed;
+    seed = (unsigned int) time((time_t *) NULL);
+#ifdef _WIN32
+    seed += _getpid();
+#else
+    seed += getpid();
+#endif
+    return seed;
+}