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.

arogue7/mdport.c

@@ -71,6 +71,7 @@
 #include <limits.h>
 #include <sys/stat.h>
 #include <signal.h>
+#include <time.h>
 
 #define MOD_MOVE(c) (toupper(c) )
 
@@ -1214,3 +1215,16 @@ md_readchar(WINDOW *win)
 
     return(ch & 0x7F);
 }
+
+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;
+}