More bug-fixes, GSASL DIGEST-MD5 now works.

Defined helper streqic() since I seem tired enough to be forgetting ==0 checks.
Deal with left-over-data-to-send correctly.
Now tested with PLAIN, CRAM-MD5, DIGEST-MD5.
For DIGEST-MD5, check for server_realm, since GSASL doesn't error out without it.