php: security bump to version 5.6.17

Bug #70976 (Memory Read via gdImageRotateInterpolated Array Index Out of
Bounds).
Bug #70755 (fpm_log.c memory leak and buffer overflow).
Bug #70661 (Use After Free Vulnerability in WDDX Packet
Deserialization).
Bug #70741 (Session WDDX Packet Deserialization Type Confusion
Vulnerability).
Bug #70728 (Type Confusion Vulnerability in PHP_to_XMLRPC_worker()).

No CVEs assigned yet.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>