* ext/json: merge JSON 1.7.7.

This includes security fix. [CVE-2013-0269]
  d0a62f3ced
  https://groups.google.com/d/topic/rubyonrails-security/4_YvCpLzL58/discussion

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39208 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/json/lib/json/add/bigdecimal.rb

@@ -4,10 +4,16 @@ end
 defined?(::BigDecimal) or require 'bigdecimal'
 
 class BigDecimal
+  # Import a JSON Marshalled object.
+  #
+  # method used for JSON marshalling support.
   def self.json_create(object)
     BigDecimal._load object['b']
   end
 
+  # Marshal the object to JSON.
+  #
+  # method used for JSON marshalling support.
   def as_json(*)
     {
       JSON.create_id => self.class.name,
@@ -15,6 +21,7 @@ class BigDecimal
     }
   end
 
+  # return the JSON value
   def to_json(*)
     as_json.to_json
   end