new API weenet_process_name()
bugfix: potentially message received when _service_new() failed or before it returned
bugfix: no backward reference saved in monitored process
changes to fix account(global pid->process mapping) related bugs:
  * separate freelist and pid->process array
  * ensure process is lived in _account_retain()
  * move _unlink() to _process_delete() to ensure it called in
      first stage
changes in scheduler to make process context-switch bookeeping possible
avoid massive first dummy context-switch
separate debug and address_sanitizer builds