Add new redirect tests; fix an html2html bug with non-English redirects.

I wrote these for change I1bd36f32a5e46b90261895e5499a0308875e5e05 but they
got lost in a forgotten branch of my repo.

The html2wt tests all appear to fail because we re-serialize the #redirect
link as [[./Main Page]] instead of [[Main Page]].

Change-Id: I997cae79216d31559fb0a3abe555a26cc41acea0
Merge "Add new redirect tests; fix an html2html bug with non-English redirects."