- Save a parallel transfer's result code only when it fails and the
  transfer is not being retried.

Prior to this change the result code was always set which meant that a
failed result could be erroneously discarded if a different transfer
later had a successful result (CURLE_OK).

Before:

> curl --fail -Z https://httpbin.org/status/404 https://httpbin.org/delay/10
> echo %ERRORLEVEL%
0

After:

> curl --fail -Z https://httpbin.org/status/404 https://httpbin.org/delay/10
> echo %ERRORLEVEL%
22

Closes #xxxx

Instead output a warning about it and continue with the defaults.

These SSL versions are typically not supported by the TLS libraries since a
long time back already since they are inherently insecure and broken. Asking
for them to be used will just cause an error to be returned slightly later.

In the unlikely event that a user's TLS library actually still supports these
protocol versions, this change might make the request a little less insecure.

Closes #6772

Update test 970 accordingly.

Reported-by: Michal Rus
Fixes #6905
Closes #6906

Signed-off-by: Victor Vieux <victorvieux@gmail.com>

Closes #6895

Closes #6881

Make sure the total amount of DL/UL bytes are counted before the
transfer finalizes. Otherwise if a transfer finishes too quick, its
total numbers are not added, and results in a DL%/UL% that goes above
100%.

Detail:

progress_meter() is called periodically, and it may not catch a
transfer's total bytes if the value was unknown during the last call,
and the transfer is finished and deleted (i.e., lost) during the next
call.

Closes https://github.com/curl/curl/pull/6840

Reviewed-by: Emil Engler
Closes #6802

Closes #6727

Make the code consistently use a single name for the size of the
"curl_off_t" type.

Closes #6702