Previously, when creating an object from inert inputs (eg:
"hb_font_create(hb_face_get_empty())") we returned the inert
empty object. This is not helpful as there are legitimate
usecases to do that.
We now never return the inert object unless allocation failed.
Tests are revised to reflect.
Should move these out of the public header...
We're "clean" of introspection warnings now. Remaining ones are about
graphite2 / freetype types not being introspectable.
Sascha Brawer
Behdad Esfahbod