Method init_with_api

test/test_fibers.cpp:18–20

    int result = 0;

    void init_with_api(em_arg_callback_func entry, void *arg) {
        emscripten_fiber_init(&context, entry, arg, c_stack, sizeof(c_stack), asyncify_stack, sizeof(asyncify_stack));
    }

    void init_manually(em_arg_callback_func entry, void *arg) {
        context.stack_base = c_stack + sizeof(c_stack);