Use recent compiler

Author: stappersg

README.md

@@ -10,7 +10,8 @@ Designed for the ATmega328p.
 
 ## Prerequisites
 
-  * A recent version of the nightly Rust compiler. Anything including or greater than `rustc 1.47.0-nightly (0820e54a8 2020-07-23)` can be used.
+  * A recent version of the nightly Rust compiler. Anything including or
+    greater than `rustc 1.63.0-nightly (fee3a459d 2022-06-05)` can be used.
   * The rust-src rustup component - `$ rustup component add rust-src`
   * AVR-GCC on the system for linking
   * AVR-Libc on the system for support libraries