Combined appends lead to fewer machine code and faster performance.
Some may even say that it makes code more readable.

Running revAddrTests over reverseaddr gives measurable improvements:

	name              old time/op  new time/op  delta
	ReverseAddress-8  4.10µs ± 3%  3.94µs ± 1%  -3.81%  (p=0.000 n=10+9)

Change-Id: I9bda7a20f802bcdffc6e948789765d04c6da04e7
Reviewed-on: https://go-review.googlesource.com/117615
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>