X time neo1 - neo2; δ: gro_flush_timeout=5µs, txc=20μs/0f/0μs-irq/0f-irq

Link and TCP* latencies are ~ same and stable.

Compared to b288e62f py timings stabilize:

ZEO		~580-1045μs	-> 585µs
NEO/pylite	~600-700μs	-> ~550-570µs	(Cpy)
NEO/pylite	~525-580μs	-> ~450µs	(Cgo)
NEO/pysql	~820-930μs	-> ~840µs	(Cpy)
NEO/pysql	~740-800μs	-> ~740µs	(Cgo)

Go timings get a bit worse:

NEO/go		~360µs		-> ~380µs	(Cpy)
NEO/go		~160µs		-> ~165-170µs	(Cgo)
NEO/go-nosha1	~140µs		-> ~150µs

Compared to 15a9ccef go+pretech128 timings stabilize:

go-go+prefetch128		~65-160µs	-> ~40-45µs, 60µs(x1)
go-go+prefetch128 (!sha1)	~60-150µs	-> ~60µs,    40µs(x1)