TODO-RELEASE: deleted 4 issues

These problems have gotten no interest/feedback from users:

-275 - Introduce a way to avoid sending USER for FTP connections
-288 - bug 3219997 curl rtmp request curl: (55) select/poll returned error

This problem is rather an autoconf bug with little user interest and it
can be worked around with an older autoconf:

-278 - "Configure  $as_echo does not work"

This problem is not fixed:

-286 - bug 3214223 Pipelined HTTP requests with a zero-length body broken