update bindgen (#210)

The immediate instigation for this was
georust/geo#1283.

Turns out bindgen [dropped the `which`
dependency](rust-lang/rust-bindgen@c03964c)
a while back.

But also, good to stay on top of the dependency updates.

Author: michaelkirk

proj-sys/CHANGES.md

@@ -1,3 +1,8 @@
+# UNRELEASED
+
+- BREAKING: Update bindgen to 0.71.1
+
+
 # 0.24.0
 
 - Update to PROJ 9.4.0 (#196) 

proj-sys/Cargo.toml

@@ -16,7 +16,7 @@ libsqlite3-sys = ">=0.28,<0.31"
 link-cplusplus = "1.0"
 
 [build-dependencies]
-bindgen = { version = "0.69", optional = true }
+bindgen = { version = "0.71.1", optional = true }
 pkg-config = "0.3.25"
 cmake = "0.1.50"
 flate2 = "1.0.24"

proj-sys/MAINTAINERS.md

@@ -18,7 +18,7 @@ The process of updating bindings looks like:
 ```
 cd proj-sys
 cargo clean
-cargo build
+cargo build --features=buildtime_bindgen
 find ../target/debug/build/proj-sys* -name bindings.rs
 ```