Remove unparsing for guarding

* With the monkeypatch to parser it this is not needed anymore.
* Mutant will NOT be released with this monkeypatch, I'll try to get it
  upstream soon.
* Performance for the mutation corpus test is greatly improved.
* Positive performance chance for regular mutant runs is visible.

lib/mutant.rb

@@ -19,6 +19,41 @@ require 'anima'
 require 'concord'
 require 'morpher'
 
+# Monkey patch to parser that needs to be pushed upstream
+module Parser
+  # AST namespace
+  module AST
+    # The AST nodes we use in mutant
+    class Node
+
+      # Return hash compatible with #eql?
+      #
+      # @return [Fixnum]
+      #
+      # @api private
+      def hash
+        @type.hash ^ @children.hash ^ self.class.hash
+      end
+
+      # Test if node is equal to anotheo
+      #
+      # @return [true]
+      #   if node represents the same code semantics locations are ignored
+      #
+      # @return [false]
+      #   otherwise
+      #
+      # @api private
+      #
+      def eql?(other)
+        other.kind_of?(self.class)
+        other.type.eql?(@type) && other.children.eql?(@children)
+      end
+
+    end # Node
+  end # AST
+end # Parser
+
 # Library namespace
 module Mutant
   # The frozen empty string used within mutant

lib/mutant/mutator/node.rb

@@ -9,18 +9,6 @@ module Mutant
     class Node < self
       include AbstractType, NodeHelpers, Unparser::Constants
 
-      # Return identity of node
-      #
-      # @param [Parser::AST::Node] node
-      #
-      # @return [String]
-      #
-      # @api private
-      #
-      def self.identity(node)
-        Unparser.unparse(node)
-      end
-
       # Define named child
       #
       # @param [Symbol] name