Remove checks for PBS_XXX.

<https://msdn.microsoft.com/en-us/library/windows/desktop/bb760820(v=vs.85).aspx>

src/msw/gauge.cpp

@@ -40,15 +40,6 @@
 // constants
 // ----------------------------------------------------------------------------
 
-// old commctrl.h (< 4.71) don't have those
-#ifndef PBS_SMOOTH
-    #define PBS_SMOOTH 0x01
-#endif
-
-#ifndef PBS_VERTICAL
-    #define PBS_VERTICAL 0x04
-#endif
-
 #ifndef PBM_SETBARCOLOR
     #define PBM_SETBARCOLOR         (WM_USER+9)
 #endif