(Qcoding_system_spec): Deleted.

(Qcoding_system_spec): Deleted.
(Vcoding_system_list, Vcoding_system_alist): New variables.
(setup_coding_system): Adjusted for the change in mule.el.
(detect_eol): Likewise.
(Fcoding_system_spec): Changed to Lisp function in mule.el.
(Fcoding_system_p): Do not call Fcoding_system_spec.
(Fread_coding_system): Give Vcoding_system_alist to
Fcompleting_read as the arg TABLE.
(Fread_non_nil_coding_system): Likewise.  Give
Vcoding_system_history to Fcompleting_read as the arg HIST.
(syms_of_coding): Deleted codes for Qcoding_system and
Fcoding_system_spec.  Set up new Lisp variables.