Specified change in Regexp :blank: POSIX expression

In Ruby < 2.2 the :blank: POSIX expression matched unicode Mongolian
vowel seperator characters.  In Ruby >= 2.2 these characters do not
match.

language/regexp/character_classes_spec.rb

@@ -141,6 +141,18 @@
     "\u{3F}".match(/[[:alpha:]]/).to_a.should == []
   end
 
+  ruby_version_is ""..."2.2" do
+    it "matches Unicode Mongolian vowel seperator characters with [[:blank:]]" do
+      "\u{180E}".match(/[[:blank:]]/).to_a.should == ["\u{180E}"]
+    end
+  end
+
+  ruby_version_is "2.2" do
+    it "doesn't match Unicode Mongolian vowel seperator characters with [[:blank:]]" do
+      "\u{180E}".match(/[[:blank:]]/).to_a.should == []
+    end
+  end
+
   it "matches Unicode space characters with [[:blank:]]" do
     "\u{1680}".match(/[[:blank:]]/).to_a.should == ["\u{1680}"]
   end