Put correct "Since:" tag in all API

[behdad]

Right now we have "1.0" for everything. Put true 0.9.x version they were introduced instead...

[behdad]

http://upstream-tracker.org/versions/harfbuzz.html might come handy for that.

[behdad]

There seem to be quite a few left. See by way of git grep 'Since: 1.0'.