[Vala] Support for exporting a callback function in windows!!

["Matías De la Puente" <mfpuente ar gmail com>]

Hello all,

It is posible to add an attibute (like '[Export]') for export a callback function in windows?
In linux work fine the callback functions but in window must add this to a callback method:

G_MODULE_EXPORT void callback_example ();

When compiling on Linux, this will have absolutely no effect, but when compiling on Windows, the macro expands to __declspec(dllexport), which marks the symbol as one to be exported, so that it can be called by gmodule.

Please this support because is important (in windows only), Thanks!!!

Matias