* ioext.h: removed scm_duplicate_port prototype.

* ioext.h: removed scm_duplicate_port prototype.

* ioext.c (scm_primitive_dup2): return the new file descriptor
instead of SCM_UNSPECIFIED, since similarity to scm_primitive_dup
is convenient.
(scm_fdopen): bug fix: don't try to make port unbuffered until its
stream has been set.
(scm_duplicate_port): deleted, there's now an implementation in
boot-9.scm.
(scm_primitive_dup2): do nothing if newfd == oldfd.

* boot-9.scm (dup->port, dup->inport, dup->outport, dup->fdes,
dup, fdes->inport, fdes->outport, port->fdes): new procedures.
(duplicate-port): was a C primitive, now it's here.
(move->fdes): allow the first argument to be a file descriptor.
Return the modified port or file descriptor (was unspecified.)