Remap NAN name

gencpp.ml

@@ -314,7 +314,7 @@ let keyword_remap name =
    | "BIG_ENDIAN" | "LITTLE_ENDIAN" | "assert" | "NULL" | "wchar_t" | "EOF"
    | "bool" | "const_cast" | "dynamic_cast" | "explicit" | "export" | "mutable" | "namespace"
    | "reinterpret_cast" | "static_cast" | "typeid" | "typename" | "virtual"
-   | "_Complex" | "INFINITY"
+   | "_Complex" | "INFINITY" | "NAN"
    | "struct" -> "_" ^ name
    | "asm" -> "_asm_"
    | x -> x