To make special newlines more explicit and visible.
Mostly in `<protocol>` sections, some in `<data*>` and `<upload>`.
Reducing the number of `tests/data/test*`:
- CRLF newlines from 21535 to 11337.
- files with mixed newlines from 1335 to 707.
Also delete empty `<protocol>` sections.
Closes#19284
With CURLOPT_TIMECONDITION set, a header is automatically added (e.g.
If-Modified-Since). Allow this to be replaced or suppressed with
CURLOPT_HTTPHEADER.
Fixes#4103Closes#4109
