Back out 13063. This changes the CGI environment we construct to just be plain wrong...

Back out 13063. This changes the CGI environment we construct to just be plain wrong, SERVER_NAME is meant to be a name after all. I have a feeling that all of this crap could be simplified, but I don't want to spend a lot of tuits changing it (and possibly breaking things for people with non-obvious behaviour changes like this one) - when those tuits could be spent on Plack stuff so that all this code dies anyway (and we do a major release so breakage can be more reasonable expected / extensively tested for). This is all possibly being _too_ paranoid here, but given the original commit didn't know what was happening / what changed _at all_, I think that's fair..