Preserve the contents of secondary reference definitions

We currently change <ref name="foo">Foo</ref> ... <ref name="foo">Foo</ref>
to <ref name="foo">Foo</ref> ... <ref name="foo" /> , because know
that the second ref tag isn't canonical and so we blank it.

Instead, we now preserve the contents of all ref tags that come after
the canonical one.

Change-Id: I45a51a879271890fe46c4184f1029f12d27af678
Merge "Preserve the contents of secondary reference definitions"