libcurl: security bump to version 7.60.0

libcurl: security bump to version 7.60.0

Drop upstream patch.

This release fixes the security issues listed below.

CVE-2018-1000300: curl might overflow a heap based memory buffer when
closing down an FTP connection with very long server command replies.

  https://curl.haxx.se/docs/adv_2018-82c2.html

CVE-2018-1000301: curl can be tricked into reading data beyond the end
of a heap based buffer used to store downloaded content.

  https://curl.haxx.se/docs/adv_2018-b138.html

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>