Bump MSRV to 1.40.0

The libloading crate is used for runtime linking
and since 0.6.0 it has a MSRV of 1.40.0

Author: KyleMayes

README.md

@@ -39,7 +39,7 @@ extern "C" {
 
 ## MSRV
 
-The minimum supported Rust version is **1.34**.
+The minimum supported Rust version is **1.40**.
 
 No MSRV bump policy has been established yet, so MSRV may increase in any release.
 

ci/script.sh

@@ -31,8 +31,8 @@ case "$BINDGEN_JOB" in
         # This test should not use Cargo.lock as it's ignored for library builds
         rm Cargo.lock
         # The MSRV below is also documented in README.md, please keep in sync
-        rustup install 1.34.0
-        cargo +1.34.0 build --lib $NO_DEFAULT_FEATURES --features "$BINDGEN_FEATURES"
+        rustup install 1.40.0
+        cargo +1.40.0 build --lib $NO_DEFAULT_FEATURES --features "$BINDGEN_FEATURES"
         ;;
 
     "integration")