composition-function-table.
(tibetan-composable-pattern): New variable.
(tibetan-subjoined-transcription-alist): Change key "R" to "+R".
(tibetan-precomposition-rule-alist): Move punctuations to
tibetan-punctuation-transcription-alist and
tibetan-obsolete-glyphs.
(tibetan-punctuation-transcription-alist): New variable.
(tibetan-obsolete-glyphs): New variable.
(tibetan-regexp): Improve the initialization code.