Fixed severe breakage of non-JS upload, presumably introduced in the 1.16 upload...

Fixed severe breakage of non-JS upload, presumably introduced in the 1.16 upload rewrite. If the user doesn't enter a destination filename, it's meant to use the name of the source file. Untested code "$wgRequest->getText('wpUploadFile')" did not work, you need to fetch from $_FILES not $_REQUEST. Code to propagate the relevant default to UploadForm was missing, readded here.

Apologies for the nodata hack, but I want to backport this to 1.16, so I don't want to make any HTMLForm.php changes if I can avoid it.