Land #7253, x64 xor encoder fix

Land fullmetalcache's fix for the x64 xor encoder

modules/encoders/x64/xor.rb

@@ -24,6 +24,14 @@ class MetasploitModule < Msf::Encoder::Xor
         }
       )
   end
+  
+  # Indicate that this module can preserve some registers
+  # ...which is currently not true. This is a temp fix
+  # until the full preserve_registers functionality is
+  # implemented. 
+  def can_preserve_registers?
+    true
+  end
 
   def decoder_stub( state )