I forgot to add the array index to the varId when iterating
over a multi-PV array.

This patch also gets rid of the ugly seq_sync_timeout hack.

This is clearer and more robust than relying on the (incidental)
truth value of a pvStat value.

This brings asynchronous pvGet to the same standard w.r.t. multi-PV
arrays as pvPut. Another slight improvement: in non-safe mode, if
a variable is not assigned to a PV, then return TRUE, so that
when testing in a condition it does not hang forever.

Another one of the long overdue re-factorings. The new header file
seq_snc.h contains all the definitions that are shared between the
snc generated code and the run-time library. What remains in seqCom.h
is the public API for C code that wants to interact with an SNL program.

Members are no longer identified with variables in the syntax. Member
selection "operators" ('.' and '->') are no longer treated as binary
operators. Instead, member selection gets a new syntax node type E_SELECT,
and members (only allowed as rhs of a member selection) are not E_VAR, but
E_MEMBER. This all works because members are not first class in C, that is
"x.(name)" is a syntax error.

This is a simple solution for the recurring annoyance of snc issuing
"undefined variable" warnings.

Declaring members in a foreign declaration becomes obsolete.

This fixes a bug that crept in when implementing the new variable
initialization code for variables with global lifetime. The problem
was that the initialization variable shadowed the global variable
in non-reentrant mode, which made the initialization a no-op.

While it was always allowed to use arbitrary expressions for the
argument to delay(), this never worked as one would expect if the
expression depended on e.g. monitored variables. The reason is that
previously the delay expression was evaluated once for all delays
appearing in conditions inside a state when the state was entered.
Later checks whether the delay has expired used the cached delay
value.
Now, delay expressions are evaluated like all other parts of the
state transition condition and seq_delay() takes a double argument
instead of a delay id. As a (transparent) side effect, if the
delay has not yet expired, the minimum time to wait for events is
adjusted. This adjustment is now more precise, since we do not store
the delay but rather the (future) time when the wakeup should happen.
The new implementation makes a lot of code obsolete which has
consequently been deleted:
- type DELAY_ID and all mentions of delay ids
- assignment of delay ids in the compiler
- the special cases FT_DELAY for the delay() builtin and
  the special E_DELAY syntax node type
- generated delay init functions
- seq_delayInit()
- clearDelays() and calcTimeout() in seq_task
- array members delay, delayExpired of struct state_set
  instead there is now double wakeupTime
- member numDelays in various structs
- assign_next_delay_id in the compiler

With foreign types we can no longer generate default initializers
in a portable way, as was done previously (in reentrant mode).
We now leave off initializers from the UserVar struct and instead
initialize the members one by one (using memcpy) from statically
initialized single values.