Former implementation of `timingSafeEqual` would allow different length; allowing a core dump.

```shell
[zeen3@zeen3 ~]$ node
Running node v10.4.1 (npm v6.1.0)
> crypto.timingSafeEqual(new BigUint64Array(32), new Uint32Array(32))
node[16304]: ../src/node_crypto.cc:5158:void node::crypto::TimingSafeEqual(const v8::FunctionCallbackInfo<v8::Value>&): Assertion `(buf_length) == (Buffer::Length(args[1]))' failed.
 1: node::Abort() [node]
 2: 0x8938b5 [node]
 3: 0x97212a [node]
 4: 0xb00989 [node]
 5: v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*) [node]
 6: 0x2dbaff1841bd
Aborted (core dumped)
[zeen3@zeen3 ~]$ node
Running node v10.4.1 (npm v6.1.0)
> crypto.timingSafeEqual(new BigUint64Array(32), new Uint32Array(64))
RangeError [ERR_CRYPTO_TIMING_SAFE_EQUAL_LENGTH]: Input buffers must have the same length
    at Object.timingSafeEqual (internal/crypto/util.js:81:11)
> crypto.timingSafeEqual(new BigUint64Array(32), new Uint32Array(32))
node[16856]: ../src/node_crypto.cc:5158:void node::crypto::TimingSafeEqual(const v8::FunctionCallbackInfo<v8::Value>&): Assertion `(buf_length) == (Buffer::Length(args[1]))' failed.
 1: node::Abort() [node]
 2: 0x8938b5 [node]
 3: 0x97212a [node]
 4: 0xb00989 [node]
 5: v8::internal::Builtin_HandleApiCall(int, v8::internal::Object**, v8::internal::Isolate*) [node]
 6: 0x128c0a5041bd
Aborted (core dumped)
[zeen3@zeen3 ~]$ 
```

Though unlikely to occur it's possible.

Add various modern ArrayBuffer based timingSafeEqual variants.

Linter length < 80
Fix one issue where I wrote the wrong amount of tests.

... please don't error this time. You have no reason to.