Add systemd socket activation for epmd.

Check for systemd libraries and headers in confgiure.
Add -systemd option enabling waiting for sockets from systemd.
test_server: Allow init_per_ function to throw skip

Allow all init_per_[suite|group|testcase] to throw (or exit)
{skip, Reason} to explicitly ignore tests without failing.

It is easier to catch it in one place instead of writing a try
in each init_per_* to return {skip, Reason}.
ose: Restore the owner of the signal

As any scheduler process can consume any message we have
to make sure that the message is owned by the scheduler
before returning it in erl_drv_ose_get_signal.
ose: Reset busy port when pdq empty
Change spawn/1 + monitor/2 to spawn_monitor/1 to avoid deadlock

crashdump_viewer:progress_pmap did sometimes hang since is spawned a
process, then monitored it and waited for a specific DOWN
message. When the process' work was very fast, it would exit before
the call to monitor and the DOWN message would contain reason 'noproc'
instead of the expected {pmap_done,Result}.

By doing spawn_monitor/1 instead, the monitor is always set before the
process exits so the deadlock is avoided.
Fix crash in crashdump_viewer when node has multiple creations

A node to which we have references to multiple instances (creations)
will have an information line in the crashdump like this:

Creation: 1 2 ...

This would earlier crash because crashdump_viewer would try to do
list_to_integer on the value after "Creation: ". This is now
corrected.

This correction also helps the case when the emulator is debug
compiled, since the line could then be

Creation: 1 (refc=1)
Improve crashdump_viewer_SUITE:start_stop test case

Instead of setting a timer and expecting all processes to be
terminated, set a monitor and wait for them to terminate.
ose: Break lmconf into one per load module
ose: Initiate stdin/stdout/stderr

Needed to get std io to work in some OSE systems where stdio
is not opened when the program starts.
ose: erlang display goes to ramlog printf
ose: Prinout errno when to_erl read fails
ose: Print faults in aio sys driver calls
ose: Yielding has to be done differently for background processes.
ose: Add ifdefs for HAVE_UDP
ose: Implement tcp inet driver for OSE

The inet driver for OSE has to handle signals instead of selects
and thus the wrappers for ready_input/output are a little bit
different. However the majority of the inet code remains the same.
ose: Fix bug when hunting for signal proxy

Sometimes the wrong signal, i.e. a read reply, would be
received from this non-selective receive.
ose: Prepare slave for running on OSE

This change relies on the assumption that all arguments before the last --
to the parent beam should be left as they are.
ose: fix for packet_bytes in fd/spawn driver.
ose: Fix erts assert failed printouts
Merge branch 'dgud/test_server/throw_skip'

* dgud/test_server/throw_skip:
  test_server: Allow init_per_ function to throw skip