(compose_glyph_string): Improve the way of deciding a script.  For a character that doesn't have script property, use the last non-latin script.
(compose_glyph_string): Improve the way of deciding a
script.  For a character that doesn't have script property, use
the last non-latin script.

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