Delete unnecessary stub stack overflow handler for cloudabi.

src/libstd/sys/cloudabi/stack_overflow.rs

@@ -1,13 +1,5 @@
 #![cfg_attr(test, allow(dead_code))]
 
-pub struct Handler;
-
-impl Handler {
-    pub unsafe fn new() -> Handler {
-        Handler
-    }
-}
-
 pub unsafe fn init() {}
 
 pub unsafe fn cleanup() {}

src/libstd/sys/cloudabi/thread.rs

@@ -4,7 +4,6 @@ use crate::io;
 use crate::mem;
 use crate::ptr;
 use crate::sys::cloudabi::abi;
-use crate::sys::stack_overflow;
 use crate::sys::time::checked_dur2intervals;
 use crate::time::Duration;
 
@@ -47,10 +46,7 @@ impl Thread {
 
         extern "C" fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
             unsafe {
-                // Next, set up our stack overflow handler which may get triggered if we run
-                // out of stack.
-                let _handler = stack_overflow::Handler::new();
-                // Finally, let's run some code.
+                // Let's run some code.
                 Box::from_raw(main as *mut Box<dyn FnOnce()>)();
             }
             ptr::null_mut()