socks5: Fix compiler warning on Windows.

Authored by werner on Jan 25 2019, 1:54 PM.

Description

socks5: Fix compiler warning on Windows.

* src/assuan-socket.c (socks5_connect): Use cast macro to get the
hightest socket number.
  • GnuPG-bug-id: T3381
  • Signed-off-by: Werner Koch <wk@gnupg.org>