Bug 50426: Strip ./ from wiki link targets

We emitted these with multiple ./ prefixes. While technically correct, this
triggered VE bug 50428. By stripping these prefixes on the way out we should
avoid this issue and generally produce cleaner output.

Also added a test to ensure these links keep working and round-trip fine.

Change-Id: I804695f9fd64eb90a61d372bce2abe1f95104179