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.
Introduce a generic lws_state object with notification handlers
that may be registered in a chain.
Implement one of those in the context to manage the "system state".
Allow other pieces of lws and user code to register notification
handlers on a context list. Handlers can object to or take over
responsibility to move forward and retry system state changes if
they know that some dependent action must succeed first.
For example if the system time is invalid, we cannot move on to
a state where anything can do tls until that has been corrected.
