generator: fixed optional array parameters
generator: public accessor in method overloads
generator: fixicate NativeStructGen

Made NativeStructGen more consistent with the way Gdk.Event
and Pango.Attribute are handled. Also increases performance
because reflection is not needed anymore to marshal these
kind of structs.
generator: redundant method in NativeStructGen
generator: fixed native struct parent
generator: fixed NativeStructGen's formatting
generator: remove bitfields from Equals/GetHashCode
generator: removed redundant allocation
generator: NativeStructGen needs to be partial