Since HTTPS is "the new normal", this update changes a lot of man page
examples to use https://example.com instead of the previous "http://..."
Closes#5969
If using the read callback for HTTP_POST, and POSTFIELDSIZE is not set,
automatically add a Transfer-Encoding: chunked header, same as it is
already done for HTTP_PUT, HTTP_POST_FORM and HTTP_POST_MIME. Update
test 1514 according to the new behaviour.
Closes#4138
