(mfont__ft_drive_gsub): Adjust prototype. (mfont__ft_drive_gpos): Extern it.
(mfont__ft_drive_gsub): Adjust prototype.
(mfont__ft_drive_gpos): Extern it.

xmirror/m17n-lib,xmirror/m17n-lib,xmirror/m17n-lib,xmirror/m17n-lib