The attached patch renames "system-process-attributes" to
"process-attributes", and adds the ability to use emacs process objects
as well as pids:

  (1) Change the signature of the system-specific
      system_process_attributes functions so that the argument is of
      type pid_t, instead of Lisp_Object, and accordingly removes the
      Lisp_Object->pid_t conversion code from those functions.

  (2) Add a "process_pid" function in process.c that contains the
      process->pid mapping code which used to be in Fsignal_process.
      process_pid also accepts straight process-ids.

  (3) Change Fsignal_process to use process_pid and remove the old
      inline code which did the same thing.

  (4) Rename Fsystem_process_attributes to Fprocess_attributes, and have
      it call process_pid to convert a process object to a pid.

  (5) Change the callers of system-process-attributes (basically proced)
      to use process-attributes instead.

-Miles