(Vinhibit_changing_match_data, search_regs_1): New vars.

(Vinhibit_changing_match_data, search_regs_1): New vars.
(looking_at_1): Don't change search_regs and last_thing_searched
if `inhibit-changing-match-data' is non-nil.
(string_match_1, search_buffer, set_search_regs): Likewise.
(syms_of_search): Add Lisp level definition for
`inhibit-changing-match-data' and set it to nil.
(boyer_moore): If `inhibit-changing-match-data' is non-nil,
compute start and end of the match, instead of using values in search_regs.