Implement "open central unrounded vowel" (ä).

Author: jmcwilliams403

packages/font-glyphs/src/letter/greek/orthography.ptl

@@ -10,6 +10,7 @@ glyph-block Letter-Greek-Orthography : begin
 	# Link localization forms
 
 	link-gr LocalizedForm.IPPH 'a'              'a/doubleStorey'
+	link-gr LocalizedForm.IPPH 'aDieresis'      'aDieresis/doubleStorey'
 	link-gr LocalizedForm.IPPH 'aRetroflexHook' 'aRetroflexHook/doubleStorey'
 	link-gr LocalizedForm.IPPH 'g'              'g/doubleStorey'
 	link-gr LocalizedForm.IPPH 'gBar'           'gScriptBar'

packages/font-glyphs/src/letter/latin/lower-a.ptl

@@ -300,5 +300,6 @@ glyph-block Letter-Latin-Lower-A : begin
 	CreateTurnedLetter 'turnAScript' 0x2C70 'AScript' HalfAdvance (CAP / 2)
 
 	CreateAccentedComposition 'aDieresis' 0xE4 'a' 'dieresisAbove'
+	CreateAccentedComposition 'aDieresis/doubleStorey' null 'a/doubleStorey' 'dieresisAbove'
+
 	CreateAccentedComposition 'aSbRsbUnderlineBelow' null 'a' 'sbRsbUnderlineBelow'
-	CreateAccentedComposition 'aRightHalfRingTR' 0x1E9A 'a' 'rightHalfCircleTR'

packages/font-glyphs/src/meta/unicode-knowledge.ptl

@@ -165,6 +165,7 @@ export : define decompOverrides : object
 
 	0x1E08 { 'CCedilla' 'acuteAbove' }
 	0x1E09 { 'cCedilla' 'acuteAbove' }
+	0x1E9A { 'a' 'rightHalfCircleTR' }
 	0x1E9C { 'longs' 'shortSlashOver' }
 	0x1EDA { 'OHorn' 'acuteAbove' }
 	0x1EDB { 'oHorn' 'acuteAbove' }