Detect and drop messages with spurious clock edges

[ppannuto]

During long traces, occasionally there will be a glitch on the CLK line, which will cause all of the data to shift by one bit.

We should be able to detect this as we expect interjections to occur on byte-boundaries, so if there's an odd number of edges, we'll know something went awry (though not where). In that case we can mark that whole message as an error and drop it.

In theory, if we're watching multiple CLK lines, we could figure this out and correct it, but that's likely too hard to be worth it.

@zhiyoong Could you upload a session when this happened? It will make testing / fixing easier [should be able to upload right to this issue by dragging & dropping a file onto the window in github].