This finishes rP24229 and rP24384.
GUI Proxy objects are now easier to specialize, code duplication is reduced, code is made safer.
In details:
- the proxy private is always the IGUIObject* pointer
- the private data is accessed through a more safe wrapper
- CreateJSObject returns an opaque type to allow easier extension & prevent errors.
- The implementation of CreateJSObject is moved near the GUI Proxy template instantiation, and both are wrapped in a convenient macro.
- The common interface no longer needs to be repeated.
- All specialisations are again put in the same file, for improved compile-time & clarity, given there are so few lines now.
- While at it, implement toSource which makes it possible to uneval components (does the same as toString though).