Add support for writing file in TAP format

[remogatto]

We really need this.

Reference: http://www.worldofspectrum.org/formats.html

[ghost]

In my opinion, GoSpeccy should feature "I/O devices". Tape I/O is one of them. Other I/O devices are: border color, sound, keyboard, joystick. So, we would have 5 device types in total. The idea is that a device is something that:

• connects to particular I/O ports
• can be unplugged

In Go, a device would be an interface type.

[remogatto]

So, according to this view, the tape device would be on a separate goroutine, right? A border color device... I'm not persuaded about that.

[ghost]

Q: So, according to this view, the tape device would be on a separate goroutine, right?
A: No. I don't see any benefit of it being a separate goroutine.

Q: A border-color device ...
A: The "border-color device" istens (via a synchronous call, no goroutine) on a specific range of ports. The feature that it can be "unmounted" is merely a consequence of handling it in the same way as all the other devices. If it is "unmounted", the emulator would stop updating the border that is being displayed in the SDL window. The only benefit is that not emulating the border results in a lower CPU usage. Thus it would be possible to run "border-intensive" games and demos on slower machines (e.g: Pandora).

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In the meantime, I am slowly working on a project trying to solve the Makefile overkill (http://github.com/remogatto/gospeccy/issues#issue/28). The solution will be similar to GOFR (http://bitbucket.org/kylelemons/gofr/wiki/Home). Technically, even now we could use GOFR to build gospeccy, although there would be some issues. Anyway, I will finish this project (maybe by the next week), at the very least we will see whether it is better or worse than GOFR.

[remogatto]

TAP support for loading was added a couple of month ago. GoSpeccy can't save in TAP format though. I'm renaming this issue according and I'm removing the "next release" label.