Add a test for a case where 6g thinks that a field is visible
Ian Lance Taylor authored
when it should not be.  I couldn't get this any simpler; the
error seems to have to do with the order of the imports in
bug2.go.

R=rsc
DELTA=26  (26 added, 0 deleted, 0 changed)
OCL=23450
CL=23482
2a4f4dd8