Some code clean up

- NgxBaseFetch:
  + use AbstractMutest instead of pthread_mutex_t
  + use AtomicInt32 type as reference
  + move Headers related function to globe ngx_psol namespace
- ps_create_request_context:
  + determine options before create NgxBaseFetch.
  + fixed possiable pipe fd leakage
  + fixed costum_options memory leak
- inline some functions