Preserve test.

changeset:   11593:f1deaf35e1d1
user:        Luuk van Dijk <lvd@golang.org>
date:        Tue Jan 17 10:00:57 2012 +0100
summary:     gc: fix infinite recursion for embedded interfaces

This is causing 'interface type loop' errors during compilation
of a complex program.  I don't understand what's happening
well enough to boil it down to a simple test case, but undoing
this change fixes the problem.

The change being undone is fixing a corner case (uses of
pointer to interface in an interface definition) that basically
only comes up in erroneous Go programs.  Let's not try to
fix this again until after Go 1.

Unfixes issue 1909.

TBR=lvd
CC=golang-dev
https://golang.org/cl/5555063