when possible substitute the access pattern

	ppi = &ppg->pp_instances[n];

with
	ppi = INST(ppg, n);

In the simulator-specific code also pp_sim_get_master() and
pp_sim_get_slave() are used. Finally pp_sim_is_master() and
pp_sim_is_slave() are used to make the conditions easier to
understand

the diagnostics messages were printed with too much newlines
because they were using the standard libc puts instead of pp_puts

the send function checks if the sent packet is
a Follow_Up. In this case it adds the jitter to the delay
of the previous Sync, to avoid the the Follow_Up to be
received before its Sync.

It sets how much time the simulator should simulate. The default value
is set to 3600 so that running the simulator without specifying the
sim_duration_sec option will result in a simulation representing an hour
of real time

This makes the diagnostics easier to understand, printing MASTER and SLAVE
for every message

Now you can assign the name you want to the interfaces, because it
doesn't really look for a physical interface with that name. This
can be useful to make the diagnostics easier to understand

so that you don't need to be administrator to run the simulator and
you don't have conflicts if there is already a PTP instance running on
the standard ports

New struct sim_pending_pkt is introduced to hold information on pakets still in
fly. An array of such structures is stored in ppg->arch_data. This array is
written by every send. The insertion is designed to sort automatically the
packets so that the first element of the array after an insertion is always
the first packet that will be received. Function sim_fast_forward_ns is changed
to update also the reception times into this array, so that when you fast
forward, also the pending packets are fast_forwarded.
The main loop works in this way:
	- if there are packets to be received check when
	- if the first packet to be received is coming before the state machine
	  timestamps expire, then fast forward till it's time to receive it.
	  Then receive it and call the state machine of the receiver
	- if there are no packet pending or the first pending packet is coming
	  after a timeout, then fast forward till the timeout expires and
	  run all the state machines

It will be used to jump ahead in time when no machine is executing.

This structure represents all the delays on the outgoing link of
the pp_instance. It will be used by the network operations

startup is changed, because we need to set the initial time for the
master before we set the initial offset from master fo the slave.
In this way the diagnostics cannot be turned on to print out the
config for the master. This is not a problem, because the master
it's not meant to be configurable

pp_sim_get_master(ppg) always returns a pointer to master pp_instance.
pp_sim_get_slave(ppg) always returns a pointer to slave pp_instance.
pp_sim_is_master(ppi) and pp_sim_is_slave(ppi) are test for obvious
conditions. these last two can be used only if ppi->glbs != NULL,
so only if a ppi has been fully initialized.

These are namely Data Sets, runtime options, servo and TimeProperties.
We need them in every instance because we have two ppi (master and slave)
acting like two different machines, so they need different copies of
these variables. We just put the per-instance stuff in the arch_data.
Then we'll change the pointers in the ppg directly in the net operations,
according to our needs.

They're designed to be used for both the instances, master and slave.
This is possible because the new data structure pp_sim_time_instance
holding all the information about the time of a single instance is
placed inside the ppi arch_data

For now it's the same as arch-unix but it will change
when we will add more configuration parameters for the
simulator. So it's better to change its name, from the
beginning

Kconfig is updated with new arch.
It compiles but it's actually doing nothing

New prototype for cfg_handler to remove the global variable *current_ppg.
The current ppg is now passed as argument to the cfg handler as follows:

typedef int (*cfg_handler)(int lineno, struct pp_globals *ppg,
				union pp_cfg_arg *arg);

New variable added in include/ppsi/pp-instance.h:

struct pp_globals_cfg {
	int cfg_items;
	int cur_ppi_n;
};

Now struct pp_globals has a new field:

struct pp_globals {
	[...]
	struct pp_globals_cfg cfg;
	[...]
};

The field cfg_items has been moved from pp_globals
to pp_globals_cfg. The configuration routine uses the field
cur_ppi_n inside pp_globals_cfg to store the current ppi being
configured. So neither the global variable *current_ppi is needed
anymore.

The helper inline function CUR_PPI has been defined to make
accesses to current ppi more readable.

As it was done also in ptp-noposix. We need to try multiple times
because sometimes it takes time for HAL to become ready (especially in
the GrandMaster mode when it has to lock SoftPLL to an ext clock).

given that INTS() is defined as inline it should not affect
the performance even in time-critical cases.

previously one could use config options without arguments, or
config options with wrong names, and the program did not complain.
now you have to use correct names for config options and only
options with type ARG_NONE can be without arguments.
hardcoded default config file and config string are supposed
always correct so there's still no error check on their parsing.
however for any config options passed from command line with -f or
-C all the checks are enabled. if there are some syntax errors or
options without value the process exits with errors, printing
informations on all the found configuration errors.

both in comments and in diagnostics

instead of bare numbers

now it reflects the definition in pp_ext_hooks. With this new prototype
you can always choose a different pp_runtime_opts to be used for the
initialization

instead to rewrite every time the checks for the parser