Fix remaining issues, move setjmp into relibc crate, move start logic into relibc

src/start.rs

@@ -1,6 +1,9 @@
 use alloc::Vec;
 use core::ptr;
 
+use header::stdio;
+use platform;
+use platform::{Pal, Sys};
 use platform::types::*;
 
 #[repr(C)]
@@ -25,7 +28,7 @@ impl Stack {
 
 #[inline(never)]
 #[no_mangle]
-pub unsafe extern "C" fn _start_rust(sp: &'static Stack) -> ! {
+pub unsafe extern "C" fn relibc_start(sp: &'static Stack) -> ! {
     extern "C" {
         fn main(argc: isize, argv: *const *const c_char, envp: *const *const c_char) -> c_int;
     }