With this change, it becomes possible to get the element type of named
slices, pointers, and channels.
This is a prerequisite to enable the common named struct types. There's
more to come.
This commit makes sure all Go types can be encoded in the interface type
code, so that Type.Kind() always returns a proper type kind for any
non-nil interface.
Package encoding/binary uses reflect and is needed by image/png, but
image/png doesn't actually need the reflect-using parts of
encoding/binary. So stub them out for now to get it to compile.
Thanks to Stephen Solka who wrote the patch.
