php: security bump to version 5.5.22

Fixes:
CVE-2015-0273 - Use after free vulnerability in unserialize() with
DateTimeZone.
CVE-2015-0235 - Mitigation for GHOST: glibc gethostbyname buffer
overflow.

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

package/php/php.hash

@@ -1,2 +1,2 @@
 # From http://php.net/downloads.php
-md5	79664ce44f7c93f355a25a3fe3dcc91b	php-5.5.21.tar.xz
+md5	fb1704131d495f5b3e6ab3b087a8dbe6	php-5.5.22.tar.xz

package/php/php.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-PHP_VERSION = 5.5.21
+PHP_VERSION = 5.5.22
 PHP_SITE = http://www.php.net/distributions
 PHP_SOURCE = php-$(PHP_VERSION).tar.xz
 PHP_INSTALL_STAGING = YES