As it turns out it can't be done automatically At least not for not GObject based libs.

I wonder if it is possible at all, since as i see it, X destroy functions are using two parameters and Vala uses one, but that may be configurable.

EDIT: Then again, HildonDesktop needs only some functions and structs to generate, maybe i can add them by hand with specific header links (most are in Xlib.h i think). This can probably create a conflict when a real X VAPI arrives.