A GDNativeLibrary now has a field "gdnative_singleton" which can be
used to let the `godot_gdnative_singleton` procedure be executed on
Godot's startup. In future this can be used to register new
scripting languages or resource importer types.
The changes include work done to ensure that GDNative apps and Nim
integration specifically can run on Android. The changes have been
tested on our WIP game, which uses godot-nim and depends on several
third-party .so libs, and Platformer demo to ensure nothing got broken.
- .so libraries are exported to lib/ folder in .apk, instead of assets/,
because that's where Android expects them to be and it resolves the
library name into "lib/<ABI>/<name>", where <ABI> is the ABI matching
the current device. So we establish the convention that Android .so
files in the project must be located in the folder corresponding to
the ABI they were compiled for.
- Godot callbacks (event handlers) are now called from the same thread
from which Main::iteration is called. It is also what Godot now
considers to be the main thread, because Main::setup is also called
from there. This makes threading on Android more consistent with
other platforms, making the code that depends on Thread::get_main_id
more portable (GDNative has such code).
- Sizes of GDNative API types have been fixed to work on 32-bit
platforms.
This adds GDNative as a separate class type.
It can be used to interface with native libraries by
using "native calls", which can be registered by modules
(and in future other GDNative libraries?).
It also reworks the currently called "GDNativeScript" into a
"NativeScript" that just makes use of the new GDNative instead
of it being the component that implements that functionality.
