Added test case 235 that makes a resumed upload of a file that isn't present

on the remote side. This then converts the operation to an ordinary STOR
upload. This was requested/pointed out by Ignacio Vazquez-Abrams.

It also proved (and I fixed) a bug in the newly rewritten ftp code (and
present in the 7.13.1 release) when trying to resume an upload and the servers
returns an error to the SIZE command. libcurl then loops and sends SIZE
commands infinitely.