Function insert

tests/std_optional.cc:9–16

#ifdef MODERN_SQLITE_STD_OPTIONAL_SUPPORT
void insert(database& db, bool is_null) {
	int id = 1;
	std::optional<int> val;
	if(!is_null) val = 5;

	db << "delete from test where id = 1";
	db << "insert into test(id,val) values(?,?)" << id << val;
}

void select(database& db, bool should_be_null) {
	db << "select id,val from test" >> [&](long long, std::optional<int> val) {