Adds missing test files to Windows installer to wrap up bpo-39459
<Compile Include="test\test_import\data\package\submodule.py" />
<Compile Include="test\test_import\data\package2\submodule1.py" />
<Compile Include="test\test_import\data\package2\submodule2.py" />
+ <Compile Include="test\test_import\data\unwritable\__init__.py" />
+ <Compile Include="test\test_import\data\unwritable\x.py" />
<Compile Include="test\test_import\__init__.py" />
<Compile Include="test\test_import\__main__.py" />
<Compile Include="test\test_index.py" />