* process.h (struct Lisp_Process): Remove filter_multibyte.

* process.h (struct Lisp_Process): Remove filter_multibyte.
* process.c (QCfilter_multibyte): Remove.
(setup_process_coding_systems): Don't use filter_multibyte.
(Fstart_process, Fmake_network_process): Don't set filter_multibyte.
(read_process_output): Don't adjust multibyteness to filter_multibyte.
(Fset_process_filter_multibyte): Change the coding-system to
approximate the previous behavior.
(Fprocess_filter_multibyte_p): Get the multibyteness straight from the
coding-system.