Add support for casting DATE values as Time objects. (:cast_dates_as_times => true)

[joe07734]

This patch adds a new query option to cast mysql DATE result values as ruby Time objects.

At Bandcamp we've been using this patch (and the other) in our fork of the mysql2 gem since the beginning. I made this patch because we use DATETIME columns in almost all our tables, but occasionally we'll use DATE. With this patch we don't have to care about mixed results.

This is a default for all our queries:

opts = Mysql2::Client.default_query_options
opts[:cast_dates_as_times] = true

I've been meaning to make these two pull requests since forever. We've had years of experience with them and think they're useful. If you have any questions about how Bandcamp's Linux/MySQL/Ruby stack works, just ask.

[sodabrew]

This is awesome! Do you have time to also ensure this works for Prepared Statements? Start with adding the same unit test with a statement, it's possible no further work is needed beyond that.

[joe07734]

Glad you dig it. I'll add the prepared statements test(s) in a bit.

[joe07734]

Added and tested.

[sodabrew]

Usually I'd squash to merge rather than keeping the history of little-edit-commits, but to preserve the two authors, would you squash down to two commits? I suggest one with the main thrust of work and the other with the fixups to get it upstreamed.

[joe07734]

It's fine by me if you squash the merge. I'm unclear how I'd squash it in the pull request, is that something you can explain?