Created attachment 305499 [details]
illustrates incorrect behavior of is_sentence_boundary

Based on http://www.unicode.org/reports/tr29/ PangoLogAttrs's is_sentence_boundary attribute is incorrect. Using http://unicode.org/cldr/utility/breaks.jsp as a visual reference we can see where the boundaries should be, but using the attached program we see that this is not the case.

Example 1:
  John said, "Sentence boundaries are broken."  Marie was not amused.

Expected:
  Sentence 1: John said, "Sentence boundaries are broken."
  Sentence 2: Marie was not amused.
Actual:
  Sentence 1: John said, "Sentence boundaries are broken."  Marie was not amused.


Example 2:
  风向转变时,有人筑墙,有人造风车。師傅領進門，修行在個人。

Expected:
  Sentence 1: 风向转变时,有人筑墙,有人造风车。
  Sentence 2: 師傅領進門，修行在個人。
Actual:
  Sentence 1: 风向转变时,有人筑墙,有人造风车。師傅領進門，修行在個人。