Use macros for working with "struct timespec" in event_queue.cc
Fix merge problem


include/my_pthread.h:
  Remove merge problem causing "struct timespec" to be declared twice
  Add macro "get_timespec_sec" used for retrieving the time in seconds
sql/event_queue.cc:
  Use macros for working with "struct timespec"
sql/log_event.cc:
  Add casts from "byte*" to "char*"