Disable blocks on OS X (rust-lang#380)

Author: KyleMayes

Changelog.md

@@ -4,7 +4,8 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
-
+### Fixed
+- Fix handling of blocks in OS X headers
 
 ## [0.19.0] - 2016-07-17
 ### Breaking

src/lib.rs

@@ -213,6 +213,9 @@ impl Default for BindgenOptions {
             args.push("-idirafter".to_owned());
             args.push(dir.to_str().unwrap().to_owned());
         }
+        if cfg!(target_os="macos") {
+            args.push("-U__BLOCKS__".to_owned());
+        }
         BindgenOptions {
             match_pat: Vec::new(),
             builtins: false,