php: security bump to version 5.5.20

Fixes:
CVE-2014-8142 - Use after free vulnerability in unserialize()

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

package/php/php.hash

@@ -1,2 +1,2 @@
 # From http://php.net/downloads.php
-md5	c63dcfd8b318d12127ba6d39ecc8a444	php-5.5.19.tar.xz
+md5	51377838dfee2d7bb4715674ac715394	php-5.5.20.tar.xz

package/php/php.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-PHP_VERSION = 5.5.19
+PHP_VERSION = 5.5.20
 PHP_SITE = http://www.php.net/distributions
 PHP_SOURCE = php-$(PHP_VERSION).tar.xz
 PHP_INSTALL_STAGING = YES