Resolve _WIN32 isnan() fiasco completely.

src/FBX2glTF.h

@@ -11,8 +11,6 @@
 #define __FBX2GLTF_H__
 
 #if defined ( _WIN32 )
-// This can be a macro under Windows, confusing FMT
-#undef isnan
 // Tell Windows not to define min() and max() macros
 #define NOMINMAX
 #include <Windows.h>
@@ -23,6 +21,11 @@ const std::string FBX2GLTF_VERSION = "0.9.5";
 #include <fmt/printf.h>
 #include <fbxsdk.h>
 
+#if defined ( _WIN32 )
+// this is defined in fbxmath.h
+#undef isnan
+#endif
+
 #include "mathfu.h"
 
 #endif // !__FBX2GLTF_H__

src/Fbx2Raw.cpp

@@ -17,6 +17,7 @@
 #include <cstdint>
 #include <cstdio>
 #include <cassert>
+#include <cmath>
 
 #include "FBX2glTF.h"
 #include "utils/File_Utils.h"