Exploit new -with_headers flag in db_list_of_lists to reimplement db_foreach in a way that only one db handle is used
Advantages: - api is now transaction safe (with respect to database operations executed in the code block) - nested db_foreach statements won't risk to occupy all available handles anymore
Possible drawbacks: - query result needs to be completely stored inside a list before looping - calling stack is now one level deeper...