#491 concatenate rls records fragments

[Jovis7]

• https://github.com/getlantern/engineering/issues/491
• In processHello(), the rrc.dataRead is the raw bytes copied from origin records buffer and not concatenated for record fragmentation.
• Add concatenation logic

[hwh33]

This mostly looks good @Jovis7, just a couple of small comments.

[hwh33]

This is working for me @Jovis7, awesome work!

To test, I ran a client configured with "tlsFrag": "index:2" against (1) a TLS proxy based off main and (2) a TLS proxy based off this branch. The client failed to connect in the first case, but worked in the second case when dialing a proxy running your changes.

Let's merge this on Monday!

[hwh33]

This was merged (and thus deployed) 18 hours ago, with no ill effect to HTTPS traffic:

We should be good to deploy record fragmentation tracks now too. Excellent work @Jovis7!