Remove more "#ifdef subprocesses".

Remove more "#ifdef subprocesses".

 process.c <inhibit_sentinels>: Move to the common part.
 (Fwaiting_for_user_input_p): Move to the common part; return nil
 if async subprocesses aren't supported.
 sysdep.c (wait_for_termination) [!MSDOS]: Don't compile on
 MS-DOS.  Remove "#ifdef subprocesses".
 (sys_subshell, sys_select): Remove "#ifdef subprocesses".
 (gettimeofday): Remove "#ifdef subprocesses".
 (wait_without_blocking): Remove function.
 (flush_pending_output, child_setup_tty): Don't compile on MS-DOS.
 Remove "#ifdef subprocesses".
 (child_setup_tty): Use WINDOWSNT instead of DOS_NT, since not
 compiled on MS-DOS.
 callproc.c (Fcall_process) [!MSDOS]: Don't call
 wait_for_termination on MS-DOS.
 emacs.c (shut_down_emacs): Remove "#ifndef subprocesses" from
 initialization of inhibit_sentinels.
 keyboard.c (record_asynch_buffer_change): Remove "#ifdef
 subprocesses" conditional.
 callproc.c (Fcall_process) [!subprocesses]: Don't call
 wait_for_termination, since `buffer' cannot be an integer when
 async subprocesses are not supported
 xdisp.c (decode_mode_spec): Use `MSDOS' instead of `subprocesses'
 for ifdefing away the call to Fprocess_status.