(Mgenerator, Mend): New variables.

(Mgenerator, Mend): New variables.
(flt_min_coverage, flt_max_coverage): New variables.
(GCPY): New macro.
(GDUP): Use it.
(Mfont_has): Renamed from Mexist.  Referrers chagned.
(gen_otf_tag): Handle the trailing whitespaces.
(otf_count_features, otf_store_features): Fix for negative features.
(parse_otf_command): Adjusted for the change of MFLTOtfSpec.
(load_otf_command): Likewise.
(free_flt_command): Adjusted for the change of MFLTOtfSpec.
(load_flt): Argument changed.  Caller changed.
(free_flt_list): New function.
(run_rule): Adjusted for the change of FontLayoutContext.
(mflt_run): Adjusted for the change of FontLayoutContext.