ipa: support syllabic breaks
x-sampa: support syllabic breaks
cxs: support syllabic breaks
cxs: standardize on non-syllabic diacritics for diphthongs
x-sampa: standardize on non-syllabic diacritics for diphthongs
x-sampa/cxs: add triphthong support
ipa: make non-syllabic diacritic transcriptions default for diphthongs
ipa: add triphthong tests
ipa: default to /ɪə̯/ for the NEAR diphthong
ipa: default to /ɛə̯/ for the SQUARE diphthong