[Accessibility] TTS API interface description + reqs update

[Jonathan Duddington]

say_text()  End of text indication.

1.  It is not specified how end-of-text is indicated.  Perhaps a zero
value character indicates end-of-text?

 
2.  Selection within the text.
Consider an application which displays SSML text.  A user selects a
portion of that text to be spoken.  How does the application indicate
the end point of the text to be spoken?  The interface doesn't provide
for an "end position". 

Does the application need to make a copy of the text, from the start of
the <speak> block, up until the end point and then add a zero character
terminator to indicate the end point?

Also, as I suggested earlier, it seems that the application needs to be
able to specify the start point as a Character position (which is not
currently provided) rather than a Word or Sentence position.

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