build: upgrade bindgen to 0.51.1

The preivous bindgen version (0.32.0) fails on Rust 1.39 (see
rust-lang/rust-bindgen#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.

Author: Daniel Dulaney

Cargo.toml

@@ -21,7 +21,7 @@ libc = "0.2"
 num_cpus = "1.0"
 cc = "1.0"
 pkg-config = "0.3"
-bindgen    = "0.51"
+bindgen    = "0.51.1"
 regex      = "0.2"
 
 [features]

build.rs

@@ -102,13 +102,17 @@ impl ParseCallbacks for IntCallbacks {
         }
     }
 
-    // https://github.com/servo/rust-bindgen/issues/687
-    // Original fix is broken with bindgen 0.51 and linux 5.2
+    // https://github.com/rust-lang/rust-bindgen/issues/687#issuecomment-388277405
     fn will_parse_macro(&self, name: &str) -> MacroParsingBehavior {
-        if name.starts_with("FP_") {
-            MacroParsingBehavior::Ignore
-        } else {
-            MacroParsingBehavior::Default
+        use MacroParsingBehavior::*;
+
+        match name {
+            "FP_INFINITE" => Ignore,
+            "FP_NAN" => Ignore,
+            "FP_NORMAL" => Ignore,
+            "FP_SUBNORMAL" => Ignore,
+            "FP_ZERO" => Ignore,
+            _ => Default,
         }
     }
 }
@@ -935,12 +939,6 @@ 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("*")