php: security bump to version 5.5.23

Fixes:
CVE-2015-0231 - Use After Free Vulnerability in unserialize()
CVE-2015-2305 - heap overflow vulnerability in regcomp.c
CVE-2015-2331 - ZIP Integer Overflow leads to writing past heap boundary

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>