Fix bug: ascs::list cannot be moved properly via moving constructor.
Use ASCS_DELAY_CLOSE instead of ASCS_ENHANCED_STABILITY macro to control delay close duration,
 0 is an equivalent of defining ASCS_ENHANCED_STABILITY, other values keep the same meanings as before.
Move ascs::socket::closing related logic to ascs::object.
Make ascs::socket::id(uint_fast64_t) private to avoid changing IDs by users.
Call close at the end of shutdown function, just for safety.
Add move capture in lambda.
Optimize lambda expressions.