ruby: security bump to version 2.2.4

Fixes:
CVE-2015-7551 - Unsafe tainted string usage in Fiddle and DL

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

package/ruby/ruby.hash

@@ -1,2 +1,2 @@
-# From https://www.ruby-lang.org/en/news/2015/08/18/ruby-2-2-3-released/
-sha256	c6ec90e9ed018e6d9a578fc93755d8565839908d5796809e1aecd1798c7ea8a7	ruby-2.2.3.tar.xz
+# From https://www.ruby-lang.org/en/news/2015/12/16/ruby-2-2-4-released/
+sha256	d28bff4641e382681c58072ddc244d025ac47ff71dd9426a92fcfc3830d1773c	ruby-2.2.4.tar.xz

package/ruby/ruby.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 RUBY_VERSION_MAJOR = 2.2
-RUBY_VERSION = $(RUBY_VERSION_MAJOR).3
+RUBY_VERSION = $(RUBY_VERSION_MAJOR).4
 RUBY_VERSION_EXT = 2.2.0
 RUBY_SITE = http://cache.ruby-lang.org/pub/ruby/$(RUBY_VERSION_MAJOR)
 RUBY_SOURCE = ruby-$(RUBY_VERSION).tar.xz