Frozen ctypes com server can't load OLE typelib

When registering a frozen inproc com server, an exception is thrown when LoadTypeLibEx is passed a c_wchar_p string instead of a unicode string.

``` python
Traceback (most recent call last):
File "", line 1, in
File "boot_ctypes_com_server.py", line 80, in DllRegisterServer
File "C:\Python34\lib\site-packages\comtypes\server\register.py", line 328, in register
Registrar().register(cls)
File "C:\Python34\lib\site-packages\comtypes\server\register.py", line 135, in register
self._register(cls, executable)
File "C:\Python34\lib\site-packages\comtypes\server\register.py", line 152, in _register
LoadTypeLibEx(dll, REGKIND_REGISTER)
File "C:\Python34\lib\site-packages\comtypes\typeinfo.py", line 485, in LoadTypeLibEx
_oleaut32.LoadTypeLibEx(c_wchar_p(szFile), regkind, byref(ptl))
TypeError: unicode string or integer address expected instead of bytes instance
DEBUG:comtypes.server.register:Unregister
```