Made sure all namespace test files get generated.

Also included them in the C++ test.

Change-Id: Ib0c8470f0aacdf16616c27494abdda57a010195d
Tested: on Linux.

tests/namespace_test/NamespaceA/NamespaceB/EnumInNestedNS.py

@@ -0,0 +1,9 @@
+# automatically generated, do not modify
+
+# namespace: NamespaceB
+
+class EnumInNestedNS(object):
+    A = 0
+    B = 1
+    C = 2
+