Remove duplicate documentation

* doc/ref/posix.texi (Ports and File Descriptors): Remove duplicate
  documentation for port-mode and setvbuf.

doc/ref/posix.texi

@@ -419,13 +419,6 @@ is made to move away ports which are using @var{newfd}.
 The return value is unspecified.
 @end deffn
 
-@deffn {Scheme Procedure} port-mode port
-Return the port modes associated with the open port @var{port}.
-These will not necessarily be identical to the modes used when
-the port was opened, since modes such as ``append'' which are
-used only during port creation are not retained.
-@end deffn
-
 @deffn {Scheme Procedure} port-for-each proc
 @deffnx {C Function} scm_port_for_each (SCM proc)
 @deffnx {C Function} scm_c_port_for_each (void (*proc)(void *, SCM), void *data)
@@ -443,26 +436,6 @@ a pointer to a C function and passes along a arbitrary @var{data}
 cookie.
 @end deffn
 
-@deffn {Scheme Procedure} setvbuf port mode [size]
-@deffnx {C Function} scm_setvbuf (port, mode, size)
-@cindex port buffering
-Set the buffering mode for @var{port}.  @var{mode} can be one of the
-following symbols:
-
-@table @code
-@item none
-non-buffered
-@item line
-line buffered
-@item block
-block buffered, using a newly allocated buffer of @var{size} bytes.
-If @var{size} is omitted, a default size will be used.
-@end table
-
-Only certain types of ports are supported, most importantly
-file ports.
-@end deffn
-
 @deffn {Scheme Procedure} fcntl port/fd cmd [value]
 @deffnx {C Function} scm_fcntl (object, cmd, value)
 Apply @var{cmd} on @var{port/fd}, either a port or file descriptor.