Bump MSRV to 1.56

once_cell v1.15 switched to the 2021 edition and thus requires at least
Rust 1.56 to build. This commit increases our MSRV accordingly.

Fixes: #756
Signed-off-by: Uli Schlachter <psychon@znc.in>

.github/workflows/CI.yml

@@ -173,7 +173,7 @@ jobs:
     - uses: actions-rs/toolchain@v1
       with:
         profile: minimal
-        toolchain: 1.46.0
+        toolchain: 1.56.0
         override: true
           #
     # build

README.md

@@ -4,7 +4,7 @@
 [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/950g0t6i8hfc9dup/branch/master?svg=true)](https://ci.appveyor.com/project/psychon/x11rb)
 [![Crate](https://img.shields.io/crates/v/x11rb.svg)](https://crates.io/crates/x11rb)
 [![API](https://docs.rs/x11rb/badge.svg)](https://docs.rs/x11rb)
-![Minimum rustc version](https://img.shields.io/badge/rustc-1.46+-lightgray.svg)
+![Minimum rustc version](https://img.shields.io/badge/rustc-1.56+-lightgray.svg)
 [![License](https://img.shields.io/crates/l/x11rb.svg)](https://github.com/psychon/x11rb#license)
 
 Feel free to open issues for any problems or questions you might have.

clippy.toml

@@ -1 +1 @@
-msrv = "1.46.0"
+msrv = "1.56.0"

x11rb-protocol/Cargo.toml

@@ -10,7 +10,7 @@ authors = [
 repository = "https://github.com/psychon/x11rb"
 readme = "../README.md"
 edition = "2018"
-rust-version = "1.46"
+rust-version = "1.56"
 license = "MIT OR Apache-2.0"
 keywords = ["xcb", "X11"]
 

x11rb/Cargo.toml

@@ -10,7 +10,7 @@ authors = [
 repository = "https://github.com/psychon/x11rb"
 readme = "../README.md"
 edition = "2018"
-rust-version = "1.46"
+rust-version = "1.56"
 license = "MIT OR Apache-2.0"
 keywords = ["xcb", "X11"]
 exclude = [