... for extracting certs from a live HTTPS server to make a cacerts.pem
from them.

... to make make the files appear in distribution tarballs

Closes #2856

- CURLOPT_HEADERFUNCTION: add newlines
- CURLOPT_INTERLEAVEFUNCTION: fix the description of 'userdata'
- CURLOPT_READDATA: mention crashes, same as in CURLOPT_WRITEDATA
- CURLOPT_READFUNCTION: rename 'instream' to 'userdata' and explain
  how to set it

Closes https://github.com/curl/curl/pull/2868

Closes #2867

Fixes #2837
Closes #2858
Reported-by: Markus Elfring

This allows the use of PKCS#11 URI for certificates and keys without
setting the corresponding type as "ENG" and the engine as "pkcs11"
explicitly. If a PKCS#11 URI is provided for certificate, key,
proxy_certificate or proxy_key, the corresponding type is set as "ENG"
if not provided and the engine is set to "pkcs11" if not provided.

Acked-by: Nikos Mavrogiannopoulos
Closes #2333

Since it will slip and the version is the important part there, not the
date.

Closes #2793

Closes #2804

Closes #2794

The statement, “The application does not have to keep the string around
after setting this option,” appears to be indented under the RTMP
paragraph. It actually applies to all protocols, not just RTMP.
Eliminate the extra indentation.

Closes #2788

For compatibility with `fwrite`, the `CURLOPT_WRITEFUNCTION` callback is
passed two `size_t` parameters which, when multiplied, designate the
number of bytes of data passed in. In practice, CURL always sets the
first parameter (`size`) to 1.

This practice is also enshrined in documentation and cannot be changed
in future. The documentation states that the default callback is
`fwrite`, which means `fwrite` must be a suitable function for this
purpose. However, the documentation also states that the callback must
return the number of *bytes* it successfully handled, whereas ISO C
`fwrite` returns the number of items (each of size `size`) which it
wrote. The only way these numbers can be equal is if `size` is 1.

Since `size` is 1 and can never be changed in future anyway, document
that fact explicitly and let users rely on it.

Closes #2787

+ The hackerone bounty and its process

- We don't and can't handle pre-notification

Apparently the C => HTML converter on the web site doesn't quite like it
otherwise.

Reported-by: Jeroen Ooms

Closes #2724

... and not the other way around, which this previously said.

Reported-by: Vasiliy Faronov
Fixes #2723
Closes #2726

When size_t is not a typedef for unsigned long (as usually the case on
Windows), GCC emits -Wformat warnings when using lu and lx format
specifiers with size_t. Silence them with explicit casts to
unsigned long.

Closes https://github.com/curl/curl/pull/2721

Closes #2706

Closes #2704

The code treated the set version as the *exact* version to require in
the TLS handshake, which is not what other TLS backends do and probably
not what most people expect either.

Reported-by: Andreas Olsson
Assisted-by: Gaurav Malhotra
Fixes #2691
Closes #2694

Reported-by: Andreas Olsson
Fixes #2692
Closes #2693

The previous example was a little bit confusing, because SSL* structure
(or other "in use" SSL connection pointer) is not accessible after the
transfer is completed, therefore working with the raw TLS library
specific pointer needs to be done during transfer.

Closes #2690

Follow-up to b6a16afa

Closes #2673

Closes #2663