rustc: Exclude #[repr(C)] from non camel case

C structs predominately do not use camel case identifiers, and we have a clear
indicator for what's a C struct now, so excuse all of them from this stylistic
lint.

src/librustc/lint/builtin.rs

@@ -744,6 +744,11 @@ impl LintPass for NonCamelCaseTypes {
             }
         }
 
+        let has_extern_repr = it.attrs.iter().fold(attr::ReprAny, |acc, attr| {
+            attr::find_repr_attr(cx.tcx.sess.diagnostic(), attr, acc)
+        }) == attr::ReprExtern;
+        if has_extern_repr { return }
+
         match it.node {
             ast::ItemTy(..) | ast::ItemStruct(..) => {
                 check_case(cx, "type", it.ident, it.span)

src/test/compile-fail/lint-non-camel-case-types.rs

@@ -32,4 +32,9 @@ enum Foo5 {
 trait foo6 { //~ ERROR trait `foo6` should have a camel case name such as `Foo6`
 }
 
+#[repr(C)]
+struct foo7 {
+    bar: int,
+}
+
 fn main() { }