package/libcurl: security bump to version 7.79.1

package/libcurl: security bump to version 7.79.1

Fixes the following security issues:

- CVE-2021-22945: UAF and double-free in MQTT sending
  When sending data to an MQTT server, libcurl could in some circumstances
  erroneously keep a pointer to an already freed memory area and both use
  that again in a subsequent call to send data and also free it again.

  https://curl.se/docs/CVE-2021-22945.html

- CVE-2021-22946: Protocol downgrade required TLS bypassed
  A user can tell curl to require a successful upgrade to TLS when speaking
  to an IMAP, POP3 or FTP server (--ssl-reqd on the command line or
  CURLOPT_USE_SSL set to CURLUSESSL_CONTROL or CURLUSESSL_ALL with libcurl).
  This requirement could be bypassed if the server would return a properly
  crafted but perfectly legitimate response.

  This flaw would then make curl silently continue its operations without
  TLS contrary to the instructions and expectations, exposing possibly
  sensitive data in clear text over the network.

  https://curl.se/docs/CVE-2021-22946.html

- CVE-2021-22947: STARTTLS protocol injection via MITM
  When curl connects to an IMAP, POP3, SMTP or FTP server to exchange data
  securely using STARTTLS to upgrade the connection to TLS level, the server
  can still respond and send back multiple responses before the TLS upgrade.
  Such multiple "pipelined" responses are cached by curl.  curl would then
  upgrade to TLS but not flush the in-queue of cached responses and instead
  use and trust the responses it got before the TLS handshake as if they
  were authenticated.

  Using this flaw, it allows a Man-In-The-Middle attacker to first inject
  the fake responses, then pass-through the TLS traffic from the legitimate
  server and trick curl into sending data back to the user thinking the
  attacker's injected data comes from the TLS-protected server.

  Over POP3 and IMAP an attacker can inject fake response data.

  https://curl.se/docs/CVE-2021-22947.html

In addition, 7.79.1 fixes a number of regressions in 7.79.0:
https://daniel.haxx.se/blog/2021/09/22/curl-7-79-1-patched-up-and-ready/

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>