Add the header <cctype> to resolve build errors in VS2017 (#495)

orm_lib/src/sqlite3_impl/Sqlite3Connection.cc

@@ -17,6 +17,7 @@
 #include <drogon/utils/Utilities.h>
 #include <drogon/utils/string_view.h>
 #include <regex>
+#include <cctype>
 
 using namespace drogon;
 using namespace drogon::orm;