Add SetErrorLog function

[c4rlo]

This function sets a callback that SQLite invokes when it detects an anomaly. See https://sqlite.org/errlog.html.

[c4rlo]

I've just rebased this.

Any word from the maintainers on this? I think this would be a good enhancement to have. Quoting the SQLite docs linked above:

This mechanism is very helpful in tracking obscure problems that occur rarely and in the field. Application developers are encouraged to take advantage of the error logging facility of SQLite in their products, as it is very low CPU and memory cost but can be a huge aid for debugging.