bootstrap_green_task uses C abi but InitFn is Rust abi

[LaoLittle]

src/reg_context.rs

// first argument is task handle, second is thunk ptr
pub type InitFn = fn(usize, *mut usize) -> !;

src/gen_impl.rs

/// the init function passed to reg_context
fn gen_init(_: usize, f: *mut usize) -> ! {

[Xudong-Huang]

Thanks! now it looks like this

pub type InitFn = extern "C" fn(usize, *mut usize) -> !;