common: Change iobuf_fdopen argument type to gnupg_fd_t.
* common/iobuf.h (iobuf_fdopen): Use gnupg_fd_t. * common/iobuf.c (iobuf_fdopen): Use gnupg_fd_t. (iobuf_sockopen): Call do_iobuf_fdopen.
- GnuPG-bug-id: T6580
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>