package/libcurl: bump version to 7.68.0

Notice that 7.68.0 includes a Windows-only security fix:

- CVE-2019-15601: SMB access smuggling via FILE URL on Windows
  https://curl.haxx.se/docs/CVE-2019-15601.html

So not applicable to Buildroot.

Update the license hash for a copyright year update:

-Copyright (c) 1996 - 2019, Daniel Stenberg, <daniel@haxx.se>, and many
+Copyright (c) 1996 - 2020, Daniel Stenberg, <daniel@haxx.se>, and many

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libcurl/libcurl.hash

@@ -1,3 +1,3 @@
 # Locally calculated
-sha256 f5d2e7320379338c3952dcc7566a140abb49edb575f9f99272455785c40e536c  curl-7.67.0.tar.xz
-sha256 8c8824f50e73a021f5dde1fccbf69685939247399a33a32abab1fa448c9ddabb  COPYING
+sha256 b724240722276a27f6e770b952121a3afd097129d8c9fe18e6272dc34192035a  curl-7.68.0.tar.xz
+sha256 db3c4a3b3695a0f317a0c5176acd2f656d18abc45b3ee78e50935a78eb1e132e  COPYING

package/libcurl/libcurl.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-LIBCURL_VERSION = 7.67.0
+LIBCURL_VERSION = 7.68.0
 LIBCURL_SOURCE = curl-$(LIBCURL_VERSION).tar.xz
 LIBCURL_SITE = https://curl.haxx.se/download
 LIBCURL_DEPENDENCIES = host-pkgconf \