Fix rktio_create_console decl

The rktio/parse.rkt grammar doesn't handle empty argument lists and
was choking on this line, before it even got to my new line adding
rktio_udp_set_receive_buffer.

Fix by following example of using `(void)` instead of `()`. Two notes:

- I forget which variation of C or C++ requires (void) instead of ().

- Strictly speaking, this commit isn't part of the theme of this PR.
  If I squash the other commits down to one, maybe I should leave this
  separate.

racket/src/rktio/rktio.h

@@ -245,7 +245,7 @@ RKTIO_EXTERN rktio_fd_t *rktio_std_fd(rktio_t *rktio, int which);
 #define RKTIO_STDOUT 1
 #define RKTIO_STDERR 2
 
-RKTIO_EXTERN void rktio_create_console();
+RKTIO_EXTERN void rktio_create_console(void);
 /* On Windows, ensures that a console is available for output. If a
    console is created for an application started in GUI mode, The
    console cannot be closed by the user until the process exits, and