(PATFETCH): Remove the translating fetch.

(PATFETCH): Remove the translating fetch.
(PATFETCH_RAW): Rename to PATFETCH.
(set_image_of_range): New fun.
(SET_RANGE_TABLE_WORK_AREA): Use it.
(regex_compile): Don't translate the pattern chars so eagerly.
Only do it when inserting an `exactn' bytecode or when handling a char-range.
(mutually_exclusive_p): Avoid empty statement.