(coding_alloc_by_making_gap): Check the case that the

(coding_alloc_by_making_gap): Check the case that the
source and destination are the same correctly.
(decode_coding_raw_text): Set coding->consumed_char and
coding->consumed to 0.
(produce_chars): If coding->chars_at_source is nonzero, update
coding->consumed_char and coding->consumed before calling
alloc_destination.
(Fdefine_coding_system_alias): Register ALIAS in
Vcoding_system_alist.
(syms_of_coding): Define `no-convesion' coding system at the tail.