As discussed with Robert Watson on the src-committers list, it is safer
to keep at least some pty(4) entries in /etc/ttys, for applications that
roll their own PTY allocation routine and only search for BSD-style
PTY's.
This means we've now just toggled the amount of entries for pts(4) and
pty(4).
Requested by: rwatson
Because we now use pts(4)-style PTY's exclusively, there is no use for
these entries in /etc/ttys. Right now the pts(4) entries only go from 0
to 255. Because we're going to touch these files anyway, increase the
number to 511.
Discussed with: philip (ex-mentor)