Windows : remove freopen(), "to keep fd = 0 busy".

a) We do not need this on Windows, and it is not clear what it does,inside
service.

b) It hinders debugging.
mysql-test-run.pl --debugger=vsjitdebugger more often than , would stop here
throwing "invalid handle" exception.

sql/mysqld.cc

@@ -5871,12 +5871,14 @@ int mysqld_main(int argc, char **argv)
                          mysqld_port,
                          MYSQL_COMPILATION_COMMENT);
 
+#ifndef _WIN32
   // try to keep fd=0 busy
-  if (!freopen(IF_WIN("NUL","/dev/null"), "r", stdin))
+  if (!freopen("/dev/null", "r", stdin))
   {
     // fall back on failure
     fclose(stdin);
   }
+#endif
 
 #if defined(_WIN32) && !defined(EMBEDDED_LIBRARY)
   Service.SetRunning();