Examples: Win32: Fix for older Windows SDK.

examples/imgui_impl_win32.cpp

@@ -411,6 +411,8 @@ typedef enum { MDT_EFFECTIVE_DPI = 0, MDT_ANGULAR_DPI = 1, MDT_RAW_DPI = 2, MDT_
 #ifndef _DPI_AWARENESS_CONTEXTS_
 DECLARE_HANDLE(DPI_AWARENESS_CONTEXT);
 #define DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE    (DPI_AWARENESS_CONTEXT)-3
+#endif
+#ifndef DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2
 #define DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 (DPI_AWARENESS_CONTEXT)-4
 #endif
 typedef HRESULT(WINAPI * PFN_SetProcessDpiAwareness)(PROCESS_DPI_AWARENESS);                     // Shcore.lib+dll, Windows 8.1