(load_category_table): If mflt_enable_new_feature is

(load_category_table): If mflt_enable_new_feature is
zero, return NULL for such categories that require the new
feature.
(parse_otf_command): If mflt_enable_new_feature is zero, return
-1.
(load_otf_command): Fix previous change.
(load_flt): Check the return value of load_category_table.
(try_otf): Renamed from run_otf_category.  Call mflt_try_otf
instead of font->drive_otf.
(run_command): Call try_otf instead of run_otf_category.
(m17n_init_flt): Initialize mflt_enable_new_feature to 0,
mflt_try_otf to NULL.
(mflt_enable_new_feature): New variable.
(mflt_try_otf): New variable.