(maint) Adds Registry::API mock module

Prior to this commit, the monkeypatching for mocks was overwriting
the win32/registry class but ommited the API module. This commit
adds that module back.

Author: mhashizume

spec/mocks/win32.rb

@@ -6,6 +6,9 @@ def keys; end
 
     def close; end
 
+    module API
+    end
+
     class HKEY_LOCAL_MACHINE
       def self.open(*); end