red-brick: Shorten constant names
red-brick: Unify names of all variables that hold a UNIX timestamp
red-brick: Add more program stdio redirection options
red-brick: Add process state error
red-brick: Add process ID parameter to get_process_state and process_state_changed

The naming scheme would require to name it process_id, but this name is
already used of the object ID of a process object. Change the naming
scheme instead and rename user_id and group_id to uid and gid, so the
process ID can be named pid.