update Libevent packege from 'stable' based to 'master'.
success to compile
patch from 'stable_libevent_socket'
confirmed in 'stable_libevent_socket' but 'master' occurs error.
add KRefTrace() and KField{Init,Set}() macro for GC
correct import package name
don't use heap for struct timeval
fix to use 'K_NULL' in KFieldInit(), KFieldSet() macros