(USHORT): New macro for "unsigned short".

(USHORT): New macro for "unsigned short".
(prepare_drive_log): Delete it.
(setup_lookup_flags): Change the type of lookup_flags.
(lookup_gsub): Change the return value.
(gstring_insert_for_gpos): Adjusted for the change of
OTF_Glyph.positioning_type.
(print_glyph_positioning): Likewise.
(lookup_gpos): Likewise. Change the return value.
(OTF_drive_gsub_internal): New arg "with_log".  Adjusted for the
change of OTF_Glyph.positioning_type.
(OTF_drive_gsub): Fix args to OTF_drive_gsub_internal.
(OTF_drive_gsub_with_log): New function.
(OTF_drive_gpos_internal): New arg "with_log".  Adjusted for the
change of OTF_Glyph.positioning_type.
(OTF_drive_gpos): Fix args to OTF_drive_gpos_internal.
(OTF_drive_gpos2): Likewise.
(OTF_drive_gpos_with_log): New function.
(OTF_drive_gsub_alternate): Fix args to OTF_drive_gsub_internal.
(OTF_iterate_gsub_feature): Adjusted for the change of
OTF_Glyph.positioning_type.
(OTF_get_drive_log): Delete it.