don't actually affect the generated output
* generator/PropertyBase.cs: new base class for fields and
properties (mostly containing code formerly in Property.cs).
* generator/Property.cs: derive from PropertyBase
* generator/FieldBase.cs: base class for fields (containing some
code formerly in Field.cs)
* generator/StructField.cs: class for struct fields (the rest of
what used to be Field.cs)
* generator/StructBase.cs: s/Field/StructField/
* gnome/Gnome.metadata: hide a few funky _get_ methods that the
generator is just now noticing, to preserve the old output.
svn path=/trunk/gtk-sharp/; revision=43896
