Merge pull request #1435 from TheBlueMatt/mingwbuild

Fix Mingw64 build (missing headers according to M$ documentation)

src/qt/guiutil.cpp

@@ -36,6 +36,8 @@
 #define NOMINMAX
 #endif
 #include "shlwapi.h"
+#include "shlobj.h"
+#include "shellapi.h"
 #endif
 
 namespace GUIUtil {