This is still not working, but the patch makes no functional change,
only turns #ifdef into if() based on '-e' command line argument.

This adds the "-e" argument (ethernet frames), currently unused,
and catches some more errors in the command line.

The spurious "if (1) {" in there is to avoid reindenting it all,
as it would prevent easy revision of the changeset. I'll reindent
in a different commit.

used OPTS(ppi) everywhere instead of ppi->rt_opts
removed rt_opts as function parameter

We now use raw sockets as default. The choice, for gnu-linux arch,
can be done by defining PP_NET_UDP or PP_NET_IEEE_802_3.
New constant PP_ETHERTYPE=0x88f7 is defined in ieee1588_types.h,
as defined in IEEE specification.

This patch is due to the fact that the code did not correctly handle
the situation of "no incoming message". Since messageType 0 is a SYNC
message type, in those cases an empty message was tried to be handled as a SYNC
message, and led to FAULTY state. This patch seemed to me the least
invasive with respect to the current code.

It is mostly inherited from ptpd-2.1.0. May be done in a better way, but
should be fine for first tests

The 'FIXME: diag' issues still needs to be uncommented

ADJ_FREQ_MAX is machine-dependent, but is used by servo.c too, so
I declare it in pptp.h as extern and define it for each platform.
Only gnu-linux is currently supported

All structs defined; pp_update_delay and pp_init_clock are the
first implemented servo functions

From now on, this macro will be used instead of ppi->rt_opts.
Old src code should be fixed too.

virtualization of Linux adjtimex system clock time adjustment