David Lillis: Patch against Text::EtText 2.3

This is a patch against EtText]], a text to HTML converter. It mostly incorporates fixes for a number of issues that have cropped up in the over the past while.

In addition, it adds in one new feature: if a link definition contains an ampersand, it will be converted to the HTML & entity, in order to help the page to validate. This only occurs if they are not already presented in that way. Authors can now merely copy-and-paste the URLs into their link definitions and not have to worry about HTML escaping there. Avoiding these sort of issues is the whole point of EtText]], so I feel that this feature fits in with the intention of the project.

The full list of changes is as follows: