This was caught by gosimple.

Fixes #98. Fixes #111.

This function can be used to interrupt an ongoing PollEvent() call,
causing that call to return an Event with type `EventInterrupt`.

Also added a demonstration of how this could work.

As noted by the initial committer it seems like a bug.

Ported from the C version of Termbox.

Add InputMouse flag, which controls the mouse button click events.

With signal-driven IO, it is possible to create a channel that signals available
input. By combining this with non-blocking IO and another channel, the problem
on Darwin _should_ be circumvented. I have not tested this on Darwin yet, but
it works on Linux.

Somehow I missed the point, where there were input and output errors. It was
more or less handled in the C version, but all of the errors are totally ignored
in the Go version. This commit adds error. The only incompatible change is
PollEvent function, you'll have to handle or ignore its second return value.

I think an ability to handle these errors is important, not very important when
running a termbox application locally, but it is important when running through
ssh on a remote host. Hopefully now it's the very last incompatible API change.

AttrReverse makes sense mostly with ColorDefault, but since now ColorDefault is
0, you can simply use AttrReverse as an only argument.

	termbox.SetCell(x, y, ch, termbox.AttrReverse, termbox.AttrReverse)

AttrReverse is a global attribute, it will be applied if foreground has it or
background has it or both.

Instead of relying on sigwinch. Two syscalls per one screen update won't hurt.

Still incomplete, but the first step of it.

It also gives me a chance to remove Fprintf dependency. It seems faster without it.