trace: remove some now unused functions

The trace_event_count, trace_event_id and
trace_event_pattern methods are no longer required
now that everything is using the iterator APIs

The trace_event_set_state and trace_event_set_vcpu_state
macros were also unused.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1475588159-30598-6-git-send-email-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>