Dev oisf 2.1dev smtp v0.6

This is the current state of the SMTP stuff.  I reverted the change that changes mime-decode.c's strncpys to strlcpys since that causes issues.  I eyeballed the strncpys to see if they all could be changed to memcpys.  Most of them looked ok, but I didn't have time to convince myself that changing them all wouldn't cause issues without making further changes.

- PR build: https://buildbot.openinfosecfoundation.org/builders/decanio/builds/3
- PR pcaps: https://buildbot.openinfosecfoundation.org/builders/decanio-pcap/builds/3