Unsafe bytes instead of bytes pool

[gobwas]

Hello!

I have tried to use (I think, the already well known) evil technique to avoid allocations and copying. This brings about -19ns to the benchmark of picking server:

BenchmarkPickServer-4           10000000           179 ns/op           0 B/op          0 allocs/op
BenchmarkPickServer-4           10000000           160 ns/op           0 B/op          0 allocs/op

I do not think that it is aka "must have" improvement, but I have made this to notice that there is some space to increase performance and reduce the code =)

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[bradfitz]

Closing as old. Shouldn't need unsafe in this package, anyway.