By default this doesn't change any existing logging behaviour at all.
But it allows you to define cmake options to force or force-disable the
build of individual log levels using new cmake option bitfields
LWS_LOGGING_BITFIELD_SET and LWS_LOGGING_BITFIELD_CLEAR.
Eg, -DLWS_LOGGING_BITFIELD_SET="(LLL_INFO)" can force INFO log level
built even in release mode. -DLWS_LOGGING_BITFIELD_CLEAR="(LLL_NOTICE)"
will likewise remove NOTICE logging from the build regardless of
DEBUG or RELEASE mode.
There are quite a few linked-lists of things that want events after
some period. This introduces a type binding an lws_dll2 for the
list and a lws_usec_t for the duration.
The wsi timeouts, the hrtimer and the sequencer timeouts are converted
to use these, also in the common event wait calculation.
