Revert r39793 "* (bug 13879) Special:EmailUser shows a form in case no user was speci...

Revert r39793 "* (bug 13879) Special:EmailUser shows a form in case no user was specified" for the moment
* Recipient name seems to be output raw into HTML form; this is insecure
* We've lost the link to the target's user page in the primary use case (followed 'email this user' link)
* Behavior if you misspell a name doesn't look very nice; you can't just fix it and resubmit the form, you have to hit 'back' from an error page and hope your browser isn't one that deletes all your form data :D