fuzzer_sys -> libfuzzer_sys

Running the fuzzing code fails right now. Changing the crate declaration to `extern crate libfuzzer_sys` makes it work properly.

fuzz/fuzzers/parse.rs

@@ -1,6 +1,6 @@
 #![no_main]
 
-extern crate fuzzer_sys;
+extern crate libfuzzer_sys;
 
 extern crate url;
 use std::slice;