Ensuring support is compiled in
-------------------------------
Tin will compile in support for PGP if it can find it.

It looks for 'pgpk' on the path
If this is found, then PGP5 support is assumed
Otherwise it looks for 'pgp' on the path
If this is found, then PGP2 support is assumed
If neither is found, then no pgp support is compiled in
If configure is called with --disable-pgp, then no pgp support is compiled in
[ The actual program run is always 'pgp', pgpk appears to be simply a test
  for PGP5 support ]

When you try to use PGP
-----------------------
PGP2 support expects pubring.pgp
PGP5    "      "     pubring.pkr

It wants to find the above in:
$HOME/.pgp/pubring.*

Or you can override this with $PGPPATH/pubring.*

If an environment var PGPOPTS is defined, then tin will use it.
