[2.3.x] + avoid generating HttpContent.Builder objects
[2.3.x] + avoid generating Transport.FlushEvent objects
[2.3.x] + configure the max write reentrants count using System property, to avoid volatile access
[2.3.x] + avoid creating Read/WriteResult Objects every time we call CompletionHandler
[2.3.x] + fix copyrights
[2.3.x] + fix for the "avoid creating Read/WriteResult Objects every time we call CompletionHandler"