build: upgrade bindgen to 0.51.1

The preivous bindgen version (0.32.0) fails on Rust 1.39 (see
https://github.com/rust-lang/rust-bindgen/pull/1627), so an upgrade is
needed.

However, the new version also breaks when enum values are also defined as
macros. Previously, this could be handled with blacklist_type, but the
recommended method is by implementing will_parse_macro and returning
Ignore for problematic enum variants. This commit implements that method
and removes the old method.

sys/Cargo.toml

@@ -18,7 +18,7 @@ libc = "0.2"
 num_cpus = "1.0"
 cc = "1.0"
 pkg-config = "0.3"
-bindgen    = "0.32"
+bindgen    = "0.51.1"
 regex      = "0.2"
 
 [features]

sys/build.rs

@@ -12,7 +12,7 @@ use std::process::Command;
 use std::str;
 
 use regex::Regex;
-use bindgen::callbacks::{IntKind, ParseCallbacks};
+use bindgen::callbacks::{IntKind, ParseCallbacks, MacroParsingBehavior};
 
 #[derive(Debug)]
 struct Library {
@@ -71,6 +71,20 @@ impl ParseCallbacks for IntCallbacks {
             None
         }
     }
+
+    // https://github.com/rust-lang/rust-bindgen/issues/687#issuecomment-388277405
+    fn will_parse_macro(&self, name: &str) -> MacroParsingBehavior {
+        use MacroParsingBehavior::*;
+
+        match name {
+            "FP_INFINITE" => Ignore,
+            "FP_NAN" => Ignore,
+            "FP_NORMAL" => Ignore,
+            "FP_SUBNORMAL" => Ignore,
+            "FP_ZERO" => Ignore,
+            _ => Default,
+        }
+    }
 }
 
 fn version() -> String {
@@ -902,12 +916,6 @@ fn main() {
     let mut builder = bindgen::Builder::default()
         .clang_args(clang_includes)
         .ctypes_prefix("libc")
-        // https://github.com/servo/rust-bindgen/issues/687
-        .blacklist_type("FP_NAN")
-        .blacklist_type("FP_INFINITE")
-        .blacklist_type("FP_ZERO")
-        .blacklist_type("FP_SUBNORMAL")
-        .blacklist_type("FP_NORMAL")
         // https://github.com/servo/rust-bindgen/issues/550
         .blacklist_type("max_align_t")
         .rustified_enum("*")