Revision 1701633

Fix svn_stream_for_stdin() and related functions for STDOUT and STDERR
that were returning streams with mark() and seek() capabilities.

STDIN, STDOUT and STDERR don't provide general support for positioning
requests.  This behavior is implementation-specific and depends on what's
passed as the corresponding handle.  For example, on Linux, apr_file_seek()
that calls lseek() internally fails with ESPIPE [1] when the descriptor is
associated with a terminal device.  As we cannot safely advertise mark()
and seek() support for these streams, don't do that.

[1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/lseek.html

* subversion/libsvn_subr/stream.c
  (svn_stream_for_stdin, svn_stream_for_stdout, svn_stream_for_stderr):
   Don't install mark and seek handlers.