"maxval" ignored by Buffer.plot

[danstowell]

In current master, I can't seem to get Buffer.plot to choose its maxval properly:

// This works fine:
((0..31) / 4).plot(maxval: nil)


// This does not respect the request to find its own maxval
q = Buffer.alloc(s, 32)
q.setn(0, (0..31) / 4)
q.plot(maxval: nil)

[danstowell]

Also, maxval for Buffer (but not for Array) now fails to let the user specify different maxval for each channel:

// This works fine:
((0..31) / 4).plot(maxval: [20, 1], numChannels: 2)

// This does not respect the request for a different maxval for each channel
q = Buffer.alloc(s, 16, 2)
q.setn(0, (0..31) / 4)
q.plot(maxval: [20, 1])

[danstowell]

I believe 57ca3e3 fixes these issues. If not please reopen...