package/libcurl: security bump version to 7.47.0

Fixes
CVE-2016-0754: remote file name path traversal in curl tool for Windows
CVE-2016-0755: NTLM credentials not-checked for proxy connection re-use

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>