Add afsconf_BuildUbikServerSecurityObjects

This new interface is specifically for use in building the server
security objects that will be used to handle ubik-internal connections
(that is, DISK_ and VOTE_).

This is the normaml set from BuildServerSecurityObjects, with a custom
rxgk server security object.  The only tokens used for ubik-internal
communication are printed tokens, so the rxgk key negotiation service
(RXGK_) should not be provided.  afsconf_GetRXGKKey is used as the
getkey function for these connections, since the cell-wide rxgk key
from KeyFileExt is used for them.

Change-Id: Id332aabcf80ed35bda36dcce92e762d46b590f47
Remove a couple more uses of libafsauthent.a

Change-Id: Ic49d2f44293c1fbe909b61d7f4c9ac7d5a3636bb
Make libafsrpc_rxgk more reasonable

Add a file rxgk_gss_stubs.c so that we can usefully link it.

Change-Id: Ib1754abf1130824ec74c890bd40139491b597e62
Build limited rxgk support into libafsrpc

Do not include a gssapi dependency, so for the most part, only
the core security class is available and only printed tokens are
possible.

Change-Id: I80eb3d68749b8ecddfa70d54fcf88b8545b2c364
Use afsconf_BuildUbikServerSecurityObjects for vl, ptserver

Accept rxgk tokens for incoming intra-ubik connections.

Change-Id: I31dca8c8db4dada1a5d3f9b193e7506fdf6ece47
Add afsconf_BuildDbServerSecurityObjects

Used to build the server security objects for database servers that
will accept the actual user RPCs (for the VL and PR services, etc.).

Change-Id: I59e6bce2c1ccf8c873bda913b28f26d9c2a49f63
Use afsconf_BuildDbServerSecurityObjects for the vl, ptserver

Change-Id: I713d78384f4d6347b17104a97ad72650ac363491
Add afsconf_ClientAuthRXGK

Always encrypts, eliminating the need for a separate 'Secure' variant.
On modern hardware the AES we'll end up doing should be faster than
our rx stack can keep up with.

Change-Id: Ib27f2799eb927ac5aa71eab94212171344dd93df
Add -rxgk option to vlserver, ptserver

Optionally use rxgk for ubik server-to-server connections, via
afsconf_ClientAuthRXGK.  All the db servers in the cell must have
been upgraded to a version that accepts rxgk ubik connections before
this option can safely be enabled.

Change-Id: Iefae46291330d2b5e05b2a2bbaec1b9150b3c892