Allows removing a few gratuitous unsafe.Pointer conversions and
parallels the type of reflect.funcType's in and out fields ([]*rtype).

Change-Id: Ie5ca230a94407301a854dfd8782a3180d5054bc4
Reviewed-on: https://go-review.googlesource.com/16163
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>