- Add MethodBind call (besides ptrcall), since vararg methods don't work
with ptrcall.
- Fix argument name in register constant function to the way it
actually is used in the engine.
- Change the integer constant type to GDNativeInt to keep it consistent.
- Fix library loading and initialization.
- Add extra methods/parameters in the interface needed by extenstions.
- Add Variant destructors and functions for extracting values and
creating Variants from values.
* Deprecates GDNative in favor of a simpler, lower level interface.
* New extension system allows registering core engine classes.
* Simple header interface in gdnative_interace.h
