[Vala] Problems with virtual extern methods.

[Yu Feng <rainwoodman gmail com>]

Dear List,

I don't think virtual extern method is precisely defined in vala; the
code produced by 0.7.2 is kinda of weird with an undefined static _real
function.

I propose for virtual extern method we do the follows:
 
(1) assume both the accessor function and the _real function as extern
symbols in the produced ccode; 
(2) the vtable is initialized in the same way as non-extern methods; the
external _real cfunction is used to fill in the table;
(3) the accessor function is declared in the public header by valac, as
done for non-virtual members.

I made a patch for this proposal under

http://bugzilla.gnome.org/show_bug.cgi?id=584400

I am wondering if anyone wants to review it.

Regards,

Yu