Do not uppercase-lint no_mangle statics

src/test/compile-fail/lint-non-uppercase-statics.rs

@@ -16,4 +16,7 @@ static foo: isize = 1; //~ ERROR static variable `foo` should have an upper case
 static mut bar: isize = 1;
         //~^ ERROR static variable `bar` should have an upper case name such as `BAR`
 
+#[no_mangle]
+pub static extern_foo: isize = 1; // OK, because #[no_mangle] supersedes the warning
+
 fn main() { }