Add rk_undumptext(), which NUL-terminates the contents it reads.
rk_undumptext(), and now also rk_undumpdata(), can read from regular and
non-regular files (e.g., ttys, pipes, devices, but -on Windows- not
sockets).
This means that `asn1_print` can now read from `/dev/stdin`, which can
be a pipe.
There's a way to set a limit on how much to read from non-regular files,
and that limit defaults to 10MB.
At any rate, the rk_dumpdata(), rk_undumpdata(), and rk_undumptext() functions
really do not belong in lib/roken but in lib/base. There are other utility
functions in lib/roken that don't belong there too. A rationalization of the
split between lib/roken and lib/base is overdue. And while we're at it -lest I
forget- it'd be nice to move all the krb5_storage functions out of lib/krb5 and
into lib/base, as those could come in handy for, e.g., implementing OpenSSH
style certificates and other things outside the krb5 universe.
The bug fixed herein almost certainly means that PKINIT was never
working on Windows, since lib/hx509 uses rk_undumpdata() to read regular
files containing certificates and keys, but then since rk_undumpdata()
was using net_read(), that can't have worked. On Windows net_read()
insists on the FD being a socket, and because of winsock, the namespaces
of socket and file descriptors on Windows are distinct.
