Runtime memory allocation optimizations

[Metater]

Use ArraySegment and buffers allocated at startup to avoid runtime memory allocations.

To any reviewers:

1. Is zeroing the messagePtr arrays in NextClient.cs and NextServer.cs necessary?
2. Is the commented out code inside of ProcessMessage() in NextCommon.cs a good way of handling oversize packets or should it stay the way it is?

Thanks!

[Metater]

By reusing the same buffer for receiving, I created a bug when messages are queued up before the connection fully begins. So all of the queued up messages keep overwriting each other, because they are not processed immediately, as they are normally.

I am working on a fix now where the queued up data is copied to new arrays.

[Metater]

The issue should be fixed now

[Metater]

@Chykary Hey, just want to make sure you see this. Thanks!

[Chykary]

Thank you and sorry for the delay! Github mails always end up in spam folder for me, got to fix that..