Created attachment 276111 [details] [review]
introspection: add some missing Returns: (nullable) annotations

Now that bug #660879 has been fixed, I'm trying to go through and add the
missing annotations.

I've never used at-spi, so I'm not too familiar with the API, but I've gone
through all of the Returns tags and, where there is text mentioning a potential
NULL return value, I've added a (nullable) annotation.  I'm sure there are
other functions which may return NULL but I doubt I have added annotations
where they aren't appropriate, so this should be safe.