It's unnecessary, and only adds visual noise; we have been fairly
inconsistent in the past, but the semi-colon-less version clearly
dominates in the code base.
https://bugzilla.gnome.org/show_bug.cgi?id=669355
If we have an input parameter (or return value) we need to use (nullable).
However, if it is an (inout) or (out) parameter, (optional) is sufficient.
It looks like (nullable) could be used for everything according to the
Annotation documentation, but (optional) is more specific.
Higher-level wrappers around GResolver. GSocketConnectable provides an
interface for synchronously or asynchronously iterating multiple
socket addresses, with GNetworkAddress and GNetworkService providing
interfaces based on hostname and SRV record resolution.
Part of #548466.
