php: security bump to version 5.6.20

php: security bump to version 5.6.20

Fixes (no CVEs yet):
Buffer over-write in finfo_open with malformed magic file.
Invalid memory write in phar on filename with \0 in name.
Parsing of tar file with duplicate filenames causes memory leak.
php_snmp_error() Format String Vulnerability.
Integer Overflow in php_raw_url_encode.

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