This provides two modules for handling SASL
* virNetSASLContext provides the process-wide state, currently
just a whitelist of usernames on the server and a one time
library init call
* virNetTLSSession provides the per-connection state, ie the
SASL session itself. This also include APIs for providing
data encryption/decryption once the session is established
* src/Makefile.am: Add to libvirt-net-rpc.la
* src/rpc/virnetsaslcontext.c, src/rpc/virnetsaslcontext.h: Generic
SASL handling code
