Fix an issue with the SAPI 5 engine's mimic method

Re: #381.

Using the MSG and POINT structures from ctypes.wintypes, rather than
defining them ourselves, makes the engine's `mimic' method function
correctly on 64-bit Python.

dragonfly/engines/backend_sapi5/engine.py

@@ -33,9 +33,8 @@
 
 import pythoncom
 from datetime         import datetime
-from ctypes           import Structure, c_long, c_int, c_uint, pointer
-from ctypes           import windll, WinError, WINFUNCTYPE
-from ctypes.wintypes  import DWORD, HANDLE, HWND, LONG
+from ctypes           import c_int, pointer, windll, WinError, WINFUNCTYPE
+from ctypes.wintypes  import MSG, POINT, DWORD, HANDLE, HWND, LONG
 
 import win32con
 from six                       import string_types, integer_types
@@ -55,18 +54,6 @@
 
 #===========================================================================
 
-class POINT(Structure):
-    _fields_ = [('x', c_long),
-                ('y', c_long)]
-
-class MSG(Structure):
-    _fields_ = [('hwnd', c_int),
-                ('message', c_uint),
-                ('wParam', c_int),
-                ('lParam', c_int),
-                ('time', c_int),
-                ('pt', POINT)]
-
 
 class MimicObserver(RecognitionObserver):
     _log = logging.getLogger("SAPI5 RecObs")