switch to Rust 2021 edition (#264)

Dockerfile

-FROM rust:1.54 AS builder
+FROM rust:1.57 AS builder
 
 WORKDIR /cwe_checker
 

README.md

@@ -44,7 +44,7 @@ If you want to build the docker image yourself, just run `docker build -t cwe_ch
 ### Local installation ###
 
 The following dependencies must be installed in order to build and install the *cwe_checker* locally:
--   [Rust](https://www.rust-lang.org) >= 1.54
+-   [Rust](https://www.rust-lang.org) >= 1.57
 -   [Ghidra](https://ghidra-sre.org/) >= 9.2
 
 Run `make all GHIDRA_PATH=/path/to/ghidra_folder` (with the correct path to the local Ghidra installation inserted) to compile and install the cwe_checker.

src/caller/Cargo.toml

@@ -2,7 +2,7 @@
 name = "cwe_checker"
 version = "0.6.0-dev"
 authors = ["Enkelmann <nils-edvin.enkelmann@fkie.fraunhofer.de>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 structopt = "0.3"

src/cwe_checker_lib/Cargo.toml

@@ -2,7 +2,7 @@
 name = "cwe_checker_lib"
 version = "0.6.0-dev"
 authors = ["Nils-Edvin Enkelmann <nils-edvin.enkelmann@fkie.fraunhofer.de>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 apint = "0.2"

src/cwe_checker_lib/src/checkers/cwe_476/state.rs

@@ -346,7 +346,6 @@ impl State {
     #[allow(dead_code)]
     pub fn to_json_compact(&self) -> serde_json::Value {
         use serde_json::*;
-        use std::iter::FromIterator;
         let register: Vec<(String, Value)> = self
             .register_taint
             .iter()

test/Cargo.toml

@@ -2,7 +2,7 @@
 name = "acceptance_tests_ghidra"
 version = "0.1.0"
 authors = ["Enkelmann <nils-edvin.enkelmann@fkie.fraunhofer.de>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 colored = "2.0"