MFC r246641: fts: Use O_DIRECTORY when opening name that might be changed by
attacker.

There are uncommon cases where fts_safe_changedir() may be called with a
non-NULL name that is not "..". Do not block or worse if an attacker put (a
symlink to) a fifo or device where a directory used to be.
MFC r248252: libc: Avoid SIGPIPE when nscd closes the connection
unexpectedly.

It is almost always a bug if nscd closes the connection unexpectedly but
programs should not be killed with SIGPIPE for it.
MFC r246824,r246952: setbuf(3): Bring BUGS section up to date.