ptyfs in sysisnt

Haven't tested your patch, but it looks good to me.  I
always end up
manually creating ptyfs, and AFAIK there is no reason why
this
shouldn't be the default.

Also, given that tmpfs hasn't been marked 'experimental' for
months, I
feel we should deprecate mfs in favor of a tmpfs /tmp.

Any dissenting opinions?

Regards,

--Blair