MDEV-4181 : ensure mysql client's beep works on all Windows systems.

Use MessageBeep, which employs sound card, rather than system speaker.
The secondary benefit is that one can use volume control for this sound
(see MySQL's Bug #17088)

client/mysql.cc

@@ -4723,7 +4723,13 @@ put_info(const char *str,INFO_TYPE info_type, uint error, const char *sqlstate)
     if (info_type == INFO_ERROR)
     {
       if (!opt_nobeep)
+      {
+#ifdef _WIN32
+        MessageBeep(MB_ICONWARNING);
+#else
         putchar('\a');		      	/* This should make a bell */
+#endif
+      }
       vidattr(A_STANDOUT);
       if (error)
       {