Remove checks for SM_XXX system metrics symbols.

<https://msdn.microsoft.com/en-us/library/windows/desktop/ms724385(v=vs.85).aspx>

src/msw/settings.cpp

@@ -223,83 +223,41 @@ static const int gs_metricsMap[] =
 
     SM_CXBORDER,
     SM_CYBORDER,
-#ifdef SM_CXCURSOR
     SM_CXCURSOR,
     SM_CYCURSOR,
-#else
-    -1, -1,
-#endif
     SM_CXDOUBLECLK,
     SM_CYDOUBLECLK,
-#if defined(SM_CXDRAG)
     SM_CXDRAG,
     SM_CYDRAG,
     SM_CXEDGE,
     SM_CYEDGE,
-#else
-    -1, -1, -1, -1,
-#endif
     SM_CXHSCROLL,
     SM_CYHSCROLL,
-#ifdef SM_CXHTHUMB
     SM_CXHTHUMB,
-#else
-    -1,
-#endif
     SM_CXICON,
     SM_CYICON,
     SM_CXICONSPACING,
     SM_CYICONSPACING,
-#ifdef SM_CXHTHUMB
     SM_CXMIN,
     SM_CYMIN,
-#else
-    -1, -1,
-#endif
     SM_CXSCREEN,
     SM_CYSCREEN,
 
-#if defined(SM_CXSIZEFRAME)
     SM_CXSIZEFRAME,
     SM_CYSIZEFRAME,
     SM_CXSMICON,
     SM_CYSMICON,
-#else
-    -1, -1, -1, -1,
-#endif
     SM_CYHSCROLL,
     SM_CXHSCROLL,
     SM_CXVSCROLL,
     SM_CYVSCROLL,
-#ifdef SM_CYVTHUMB
     SM_CYVTHUMB,
-#else
-    -1,
-#endif
     SM_CYCAPTION,
     SM_CYMENU,
-#if defined(SM_NETWORK)
     SM_NETWORK,
-#else
-    -1,
-#endif
-#ifdef SM_PENWINDOWS
     SM_PENWINDOWS,
-#else
-    -1,
-#endif
-#if defined(SM_SHOWSOUNDS)
     SM_SHOWSOUNDS,
-#else
-    -1,
-#endif
-    // SM_SWAPBUTTON is not available under CE and it doesn't make sense to ask
-    // for it there
-#ifdef SM_SWAPBUTTON
     SM_SWAPBUTTON,
-#else
-    -1,
-#endif
     -1   // wxSYS_DCLICK_MSEC - not available as system metric
 };