Changed tree generation to correctly use PARAMOUT instead
of PARAM.

Emit Func.Exit before any returns.

Change-Id: I2fa53cc7fad05fb4eea21081ba33d1f66db4ed49
Reviewed-on: https://go-review.googlesource.com/15610Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>