Add C Closures

[akrieger]

This allows C objects to be attached to functions, and it also allows C code to be notified when these functions are finalized.

Import of https://github.com/tbluemel/quickjscpp/blob/98bf1ddb00e39d93840c4b67211c9260943b5a83/patches/2024-01-13/0001-Add-C-Closures.patch. Trivial renaming of functions and function annotations to match local style.

Closes #1212. Closes tbluemel/quickjscpp#3.

[saghul]

Thank you! Could you please add a test to api-test.c?

[bnoordhuis]

For consistency with e.g. JS_SetModuleLoaderFunc:

Suggested change

	JSValue JS_NewCClosure(JSContext *ctx, JSCClosure *func,
	int length, int magic, void *opaque,
	void (*opaque_finalize)(void*))
	JSValue JS_NewCClosure(JSContext *ctx, JSCClosure *func,
	void (*opaque_finalize)(void*),
	int length, int magic, void *opaque)

And I'd add a typedef for the finalizer callback.

[akrieger]

I'll defer to your judgement here, but after implementing it, it feels awkward to separate the finalizer from the data pointer. Other apis which accept opaque pointers do not have to manage the lifecycle of that pointer. Keeping the opaque_finalize argument last keeps the first 5 arguments consistent with the related JS_CFunction* apis.

[akrieger]

JS_EXTERN JSValue JS_NewCFunctionData2(JSContext *ctx, JSCFunctionData *func,
                                       const char *name,
                                       int length, int magic, int data_len,
                                       JSValueConst *data);
typedef void JSCClosureFinalizerFunc(void*);
JS_EXTERN JSValue JS_NewCClosure(JSContext *ctx, JSCClosure *func,
                                 const char* name,
                                 int length, int magic,
                                 void* opaque,  JSCClosureFinalizerFunc *opaque_finalize);

[akrieger]

Ooops forgot the test.