Merge pull request #71 from darksylinc/mingw-fix

Fix build errors in mingw

Author: adam-sawicki-a

src/D3D12MemAlloc.cpp

@@ -33,6 +33,12 @@
     #include <shared_mutex>
 #endif
 
+#if !defined(_MSC_VER)
+#include <guiddef.h>
+// guiddef.h must be included first.
+#include <dxguids.h>
+#endif
+
 ////////////////////////////////////////////////////////////////////////////////
 ////////////////////////////////////////////////////////////////////////////////
 //