The tftpd test server now logs all received options and thus all TFTP
test cases need to match them exactly.
Extended test 283 to use and verify --tftp-blksize.
... this also makes sure that the progess callback gets called more
often during TFTP transfers.
Added test 1238 to verify.
Bug: http://curl.haxx.se/bug/view.cgi?id=1269
Reported-by: Jo3