Add loop syntactic sugar; errors now use print instead of debug; add check for duplicate labels.

crsn_stdio/src/lib.rs

@@ -14,7 +14,6 @@ use std::io;
 use crsn::asm::instr::cond::Flag;
 use std::fmt;
 use crsn::asm::data::Wr;
-use std::time::Instant;
 
 mod console {
     use std::{io};
@@ -23,7 +22,7 @@ mod console {
     use std::ffi::c_void;
     use std::mem::{self, MaybeUninit};
     use crsn::runtime::fault::Fault;
-    use std::time::{Duration, Instant};
+    use std::time::{Instant};
 
     struct ReadCharState {
         bytes: [u8; 4],