Correctly observe availability of std::any

`std::any` is only available starting with a C++17 library.

Author: trueqbit

examples/any.cpp

@@ -14,7 +14,17 @@
  *  BLOB is mapped to std::vector<char>.
 */
 #include <sqlite_orm/sqlite_orm.h>
+#ifdef __has_include
+#if __has_include(<any>)
 #include <any>
+#endif
+#endif
+
+#if __cpp_lib_any >= 201606L
+#define ENABLE_THIS_EXAMPLE
+#endif
+
+#ifdef ENABLE_THIS_EXAMPLE
 #include <iostream>
 #include <cstdio>
 
@@ -128,8 +138,10 @@ namespace sqlite_orm {
         }
     };
 }
+#endif
 
 int main() {
+#ifdef ENABLE_THIS_EXAMPLE
     struct Value {
         int id = 0;
         std::any value;
@@ -151,5 +163,6 @@ int main() {
         cout << storage.dump(test) << endl;
     }
     cout << endl;
+#endif
     return 0;
 }