[cppia] Fix haxe overridden scriptable methods

[tobil4sk]

This enables an alternate solution for these bugs:
HaxeFoundation/haxe#12374
HaxeFoundation/haxe#12376

With this PR, haxe is able to mark methods as overrides so that they don't add an additional slot to the vtable. This way, haxe can still include them in __scriptableFunctions so that they can be resolved correctly in super.method calls, avoiding #1150.

Alternatively, if the haxe version is old and does not mark them, then fallback logic is used to infer overrides from matching method names. This has a runtime cost but avoids incorrect behaviour for current haxe. This only really affects 4.3.7 as older versions suffered from #1150.

[Simn]

Out of curiosity, where does the data functions points to actually come from? I went looking for that because these for-loops clearly assume zero-termination, but the only thing I found is the static __scriptableFunctions which is used in HX_SCRIPTABLE_REGISTER_CLASS.

[tobil4sk]

__scriptableFunctions is generated by gencpp (e.g. here) for each class/interface, and is passed in via HX_SCRIPTABLE_REGISTER_CLASS into:

hxcpp/src/hx/cppia/HaxeNative.cpp

Line 175 in 596badd

HaxeNativeClass *registered = new HaxeNativeClass(inName.utf8_str(),inDataOffset, inFunctions,inFactory, inConstruct);

So gencpp makes sure these are 0 terminated.

[Simn]

__scriptableFunctions is generated by gencpp (e.g. here) for each class/interface

Aah, that's the piece I was missing, thanks!