[hangul] Apply the appropriate *jmo features to decomposed syllables, including Old Hangul sequences that don't have Unicode compositions. Merge clusters in decomposed syllables.
[hangul] Reorder Hangul tone mark to beginning of syllable, unless font implements it using a zero-width glyph.
[unicode] Exclude the Jamo Filler characters from Default_Ignorable, as some fonts want these to be visible/spacing glyphs.
[hangul] Don't force zero-width for marks - this is not wanted for the Jamo Filler glyphs.
[hangul] Fix ordering of dotted circle with Hangul tone mark (reported by Dohyun Kim).
Merge pull request #13 from jfkthame/hangul-shaper

Tone-mark reordering and improved Old Hangul support