Add a #[macro_use] on the alloc import for format!()

Author: TheBlueMatt

lightning/src/lib.rs

@@ -31,6 +31,7 @@
 #![cfg_attr(all(any(test, feature = "_test_utils"), feature = "unstable"), feature(test))]
 #[cfg(all(any(test, feature = "_test_utils"), feature = "unstable"))] extern crate test;
 
+#[macro_use]
 extern crate alloc;
 extern crate bitcoin;
 extern crate core;