Use same bindgen dep as libnfs-sys

This avoids a cargo issue rust-lang/cargo#5237 which prevents different build scripts using different versions of libclang-sys.

Author: jsgf

Cargo.toml

@@ -13,7 +13,7 @@ keywords = ["ffi", "libffi", "closure", "c"]
 [dependencies]
 
 [build-dependencies]
-bindgen = "0.31.3"
+bindgen = "0.40.0" # match libnfs-sys bindgen dep
 make-cmd = "0.1"
 pkg-config = "0.3.13"