• Various links fixed to point to class documentation rather than its
   constructor documentation (this is a quirk of Valadoc; if using
   “{@link ClassName}” inside a method of ClassName, the link will point to
   ClassName’s constructor because symbols are resolved relatively and the
   class’ constructor is called “ClassName”).
 • Various bits of documentation expanded (mostly trivially) to shut gtk-doc
   up about missing long descriptions.
 • Some Vala code attributes moved around so the documentation comments are
   correctly associated with the code. (This shouldn’t change the behaviour
   of the attributes themselves.)
 • Some trivial constructors added to classes in order to give them
   documentation.
 • Constructor for Utils added and deprecated immediately. Utils should
   become a nested namespace on the next API break, since it will only ever
   contain static methods, and thus doesn’t need to be instantiable (which
   folks will make it at the moment).