(Note: should be removed later / merged into ipaaca-tester-cpp).

Read access in locked payloads is performed on queued operations
before searching the old database. Threads other than the locking
thread consistently read the old information.

On POSIX, default Lock now also uses boost::thread (instead of pthread)
pthread linkage is still present for legacy wrapping.

ATTENTION: unlocked payload writing is (by design) not thread-safe
(won't crash but data might be inconsistent). Please use Locker armors
around all code that might modify a payload in more than one thread.
---> #1: Always use Locker in IU handlers that write to existing IUs!!

Use with Locker, possible in a dedicated stack frame, like this:
// ... code ...
{ // open stack frame
	Locker locker(iu->payload());
	iu->payload()["a"] = "string";
	iu->payload()["b"] = "simultaneouslySentString";
} // close stack frame, sending the update

Also renamed some functions (preserving old names as deprecated aliases)

Address mode must be selected explicitly using as_map/as_list, like so:
  for (auto value: iu->payload()["listItem"].as_list()) { .... }
  for (auto kv_pair: iu->payload()["mapItem"].as_map()) { .... }
Generic size() function (reports 0 for non-structured types)

PayloadTypeConversionError thrown if (trimmed) string parse is
incomplete; comparison operators == and != catch this error though.

Setting default channel name and default payload type works OK

Sniffer: only display quotes for string-type payload values
Injector: using unicode() and catching errors

TODO: compatibility with STR legacy payloads; more varied
access to inner payload objects (e.g. push_back)