(search_buffer): Handle bytes vs chars in non-RE case.

(search_buffer): Handle bytes vs chars in non-RE case.
Have two locals len and len_byte.

(fast_c_string_match_ignore_case): Use string_make_unibyte.

(compile_pattern): New arg MULTIBYTE.  Callers changed.

(wordify): Use make_uninit_multibyte_string.
Scan by chars and bytes.

(string_match_1): Convert string indices to/from bytes.
(Freplace_match): Convert string indices to/from bytes.
(Fregexp_quote): Convert string indices to/from bytes.