Implement the GSS-API credential store API extensions defined by MIT here:
https://k5wiki.kerberos.org/wiki/Projects/Credential_Store_extensions
Note: we kill off gss_acquire_cred_ext() here. This was never a public API,
although mechanisms could have implemented it and I briefly used it in my
BrowserID prototype mechanism. gss_acquire_cred_ext_from() occupies the place
in the dispatch table where gss_acquire_cred_ext() used to, but this structure
was never visible outside Heimdal (i.e. it is only used by internal
mechanisms);
(Mechanisms that need to accept arbitrary key/value dictionaries from
applications should now implement gss_acquire_cred_from().)
restore correct OID for GSS_C_PEER_HAS_UPDATED_SPNEGO, this should have no
ABI implications, it's for internal use only. The current OID was incorrectly
copied in commit dbeeb18a, it should belong to 1.3.6.1.4.1.5322.19 which is
... enterprise(1) padl(5322) gssKrb5Extensions(19). The OID we were camping
on belongs to another party.
