Changes to satisfy dialyzer. Including changing the definition
of some of the behaviours (use the '-callback' attribute instead
of an explicit behaviour_info/1 function).

Also found and corrected some (apparently minor) bugs.

OTP-15932

Make target (for running dialyzer on snmp), os usage
and a minor snmp_log ("future proofing").

OTP-15932

Removed the use of the deprecated erlang:stacktrace() function.
Instead make use of the 'catch Class:Error:Stacktrace' feature.

OTP-15332

There no timestamp type in os (but there is in erlang).

Added common (formated) timestamp function(s). Made use of
these in the verbosity module (for debug printouts) and in
the test suite(s).

I also *think* I found the cause for some if the test case
failures (timeouts).
For v3 (agent) test cases the test manager makes use of parts
of the agent code: snmp_framework_mib and snmp_user_based_sm_mib.
And since they store their data in snmpa_local_db, that also
needs to be running.
And this was the problem (I think). On some (slow) machines,
the snmpa_local_db process from the *previous* test case
might still be running when the we tried to start it. That meant
that no new snmpa_local_db was started. Instead the old one,
still running but terminating, was retain. For a while. Until
it actually finally stopped. So the next operation towards
snmpa_local_db, insert, simply hanged until the process
terminated.
This in combination with the fact that the packet server process,
which was started using proc_lib, previously called init_ack
before this init was actually done, could actually start and then
at a much later time hang because some operation timed out
(the packet server was hanging).

Yuckety yuck-yuck.

The agent test manager had a bug during start that could
potentially cause deadlock, but atleast could cause test
cases to fail because of timeouts. The test manager
(actually the "packet server") used proc_lib to start the
process but it called the init_ack function before the init
was actually complete. This was only a problem for v3 cases
(where it did a bunch of further inits, including starting
the local-db process).

Also did debug/verbosity tweaking. Added a bunch of debug
(verbosity) printouts for the agent test manager "packet server"
during v3 init. Also made sure we could distinguish the
"normal" local-db from the one used by the test manager
(this is done by using a new short-name).

Also fixed case clause.

OTP-15287 (ERIERL-206)

OTP-15287 (ERIERL-206)

If conversion of an Audit Trail Log (ATL) entry failed,
this could result in an abort of the entire conversion,
not just the one entry. This has now been improved so
that the failure now results in a "error message" into
the "stream". Furthermore, we now keep track of the number
of entries we succeede and fail to convert.

OTP-15287 (ERIERL-206)