[HarfBuzz] please remove U+115F U+1160 from default_ignorable

[Dohyun Kim]

Hi,

While testing new version of xetex which uses harfbuzz-ng for opentype
rendering, I have encountered a serious issue about Hangul Jamo
typesetting.  The reason is that U+115F and U+1160 are assigned to
"default_ignorable" code points in hb-unicode-private.hh.

Certainly, according to unicode standard, these two characters are
Default_Ignorable_Code_Point.  However, although the exact meaning of
"default ignorable code point" is not always clear to me, I am 100%
sure that these two characters should not be ignored in opentype
rendering.

Any Hangul fonts currently available gives wrong output with current
version of harfbuzz-ng.  Take any font supporting Hangul Jamo, eg.
malgun.ttf in windows 8, jieubsida otf at
http://sourceforge.jp/projects/tsukurimashou/, unbatang ttf at
http://kldp.net/projects/unfonts/, or HCR-LVT fonts which is currently
not accessible but was avaliable at
http://ftp.ktug.or.kr/KTUG/hcr-lvt/.  Then run hb-shape --script=hang
with input string "U+115F U+1161 U+112B U+1160".  We get three
zero-width glyphs instead of two; this is wrong.

So please remove U+115F and U+1160 from default_ignorable code points,
whatever the unicode standard says about them.

Regards,
--
Dohyun Kim
College of Law, Dongguk University
Seoul, Republic of Korea