Look at explicit port for cross-origin detection

[brunosedler]

Bug description

By default, unpoly does not follow links if the href does not contain the current application host. However, hrefs that contain a port do not match the application-host-regex and are therefore not followed by unpoly by default.
The crossOrigin function needs to be adapted accordingly.

Expected behavior

Links to the same domain, that also include a port in the href should also be followed by unpoly.

[triskweline]

Links to the same domain, that also include a port in the href should also be followed by unpoly.

The port must match that of the document. A different port would constitute a different origin and cannot be followed by Unpoly.