add changelog entry and remove unused stuff

extern crate statements are not needed anymore, cfg_if was unused,
remove unused import

Author: antonilol

changelog.md

@@ -3,6 +3,8 @@ when upgrading from a version of rust-sdl2 to another.
 
 ### v0.39.0
 
+[PR #1516](https://github.com/Rust-SDL2/rust-sdl2/pull/1516) **BREAKING CHANGE** Add pregenerated bindings for Windows and Mac OS, clean bindings (remove unused aliases to integer types), update bindings.
+
 [PR #1507](https://github.com/Rust-SDL2/rust-sdl2/pull/1507) **BREAKING CHANGE** Add binding for `SDL_ComposeCustomBlendMode`. This should only be a breaking change for users relying on internal details of `BlendMode` and `SDL_BlendMode`.
 
 [PR #1510](https://github.com/Rust-SDL2/rust-sdl2/pull/1510) Fix clippy warnings.

sdl2-sys/Cargo.toml

@@ -41,7 +41,6 @@ optional = true
 
 [build-dependencies]
 version-compare = "0.1"
-cfg-if = "^1.0"
 
 [features]
 

sdl2-sys/build.rs

@@ -1,22 +1,12 @@
 #![allow(unused_imports, dead_code, unused_variables)]
 
-#[cfg(feature = "bindgen")]
-extern crate bindgen;
-#[macro_use]
-extern crate cfg_if;
-#[cfg(feature = "bundled")]
-extern crate cmake;
-#[cfg(feature = "pkg-config")]
-extern crate pkg_config;
-
 #[cfg(all(
     update_pregenerated_bindings,
     not(feature = "bindgen"),
     not(feature = "bundled"),
 ))]
 compile_error!("Enable 'bindgen' and 'bundled' features when using update_pregenerated_bindings");
 
-use std::io::ErrorKind;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::{env, fs, io};