Fix some doc build warnings

Removed references to pop3_terminate (that event was removed in a previous
commit).
Merge branch 'fastpath'
Fix a doc reference to ssl_encrypted_heartbeat.

That event isn't exported, instead the content type of
ssl_encrypted_data, which is exported, can be inspected for heartbeats.
Fix a couple of doc build warnings
change validation return value from count to int. Scripts already had been updated, I forgot the function returns..
Update submodules and NEWS.
Merge branch 'fastpath'