remove extern crate declaration and fix outfall (macros now need to be imported into scope)

using use declarations in main.rs so that use paths don't need to be updated as well, this will be done in a later commit

src/main.rs

@@ -1,43 +1,35 @@
-extern crate blake2;
-extern crate chrono;
-extern crate cpu_time;
-extern crate crossterm;
-extern crate divrem;
-#[macro_use]
-extern crate downcast;
-extern crate git_version;
-extern crate hostname;
-extern crate indexmap;
-#[macro_use]
-extern crate lazy_static;
-extern crate libc;
-extern crate native_tls;
-extern crate nix;
-extern crate openssl;
-extern crate ordered_float;
-#[macro_use]
-extern crate prolog_parser_rebis;
-#[macro_use]
-extern crate ref_thread_local;
-extern crate ring;
-extern crate ripemd160;
-#[cfg(feature = "rug")]
-extern crate rug;
-#[cfg(feature = "num-rug-adapter")]
-extern crate num_rug_adapter as rug;
-extern crate rustyline;
-extern crate sha3;
-extern crate unicode_reader;
+use blake2;
+use chrono;
+use cpu_time;
+use crossterm;
+use divrem;
+use downcast;
+use git_version;
+use indexmap;
+use lazy_static;
+use native_tls;
+use nix::sys::signal;
+use openssl;
+use ordered_float;
+use prolog_parser_rebis;
+use ref_thread_local;
+use ring;
+use ripemd160;
+use rustyline;
+use sha3;
+use unicode_reader;
 
-use crate::nix::sys::signal;
+#[cfg(feature = "num-rug-adapter")]
+use num_rug_adapter as rug;
+#[cfg(feature = "rug")]
+use rug;
 
 #[macro_use]
 mod macros;
 mod allocator;
 mod arithmetic;
-mod machine;
-mod codegen;
 mod clause_types;
+mod codegen;
 mod debray_allocator;
 mod fixtures;
 mod forms;
@@ -46,17 +38,18 @@ mod heap_print;
 mod indexing;
 mod instructions;
 mod iterators;
+mod machine;
 mod read;
 mod targets;
 mod write;
 
-use machine::*;
 use machine::streams::*;
+use machine::*;
 use read::*;
 
 use std::sync::atomic::Ordering;
 
-extern fn handle_sigint(signal: libc::c_int) {
+extern "C" fn handle_sigint(signal: libc::c_int) {
     let signal = signal::Signal::from_c_int(signal).unwrap();
     if signal == signal::Signal::SIGINT {
         INTERRUPT.store(true, Ordering::Relaxed);