Make ktc_curpag generally available

Make ktc_curpag generally available

ktc_curpag isn't specific to a Kerberos v4 environment, so move it outside
the AFS_KERBEROS_ENV #ifdef.  Add it to the auth.h header and to the
exports from the shared libafsauthent.

FIXES 125155

Reviewed-on: http://gerrit.openafs.org/64
Verified-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit cd37fd33f70c2196ff64188e32ff759590cb3748)
Reviewed-on: http://gerrit.openafs.org/208
Tested-by: Derrick Brashear <shadow@dementia.org>