curl: Fix CVE-2021-22924 and CVE-2021-22925

curl: Fix CVE-2021-22924 and CVE-2021-22925

curl v7.78 contained fixes for five CVEs:

CVE-2021-22922[1] and CVE-2021-22923[2] are only present when support
for metalink is enabled. EXTRA_OECONF contains "--without-libmetalink"
so these fixes are unnecessary.

CVE-2021-22926[3] only affects builds for MacOS.

CVE-2021-22924[4] and CVE-2021-22925[5] are both applicable. Take the
patches from Ubuntu 20.04 curl_7.68.0-1ubuntu2.6 package which is close
enough that the patch for CVE-2021-22924 applies without conflicts..

[1] https://curl.se/docs/CVE-2021-22922.html
[2] https://curl.se/docs/CVE-2021-22923.html
[3] https://curl.se/docs/CVE-2021-22926.html
[4] https://curl.se/docs/CVE-2021-22924.html
[5] https://curl.se/docs/CVE-2021-22925.html

Signed-off-by: Mike Crowe <mac@mcrowe.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>