sim: mcuboot-sys: More idiomatic Rust 2018

Apply the changes suggested by

    cargo fix --edition-idioms

and cleanup the results a bit.  Eliminate `macro_use` extern crates.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/sim/mcuboot-sys/src/c.rs b/sim/mcuboot-sys/src/c.rs
index dc73134..d623ef9 100644
--- a/sim/mcuboot-sys/src/c.rs
+++ b/sim/mcuboot-sys/src/c.rs
@@ -2,6 +2,7 @@
 
 use crate::area::AreaDesc;
 use simflash::SimFlashMap;
+use lazy_static::lazy_static;
 use libc;
 use crate::api;
 use std::sync::Mutex;