[iochk] Use printf instead of the system log.

This is a command line tool so using the system log is kind of overkill.
On the other hand, it may actually interfere with using the tool.

ZX-2681 #done
Test: iochk -> should display a message on the console.

Change-Id: Id6be2eaa774bc0ca944335dd3b508175c8217931

[zircon-internal] Move fnv1a out of zircon/public

We don't need to expose this hash function in the Zircon system
interface. We can put it in a library instead.

Test: Compiles.
Change-Id: I3a6f63997f845cf5ae78f969326d3e650950601d

[iochk] Refactor to work with skip-block.

iochk only works with block devices. Since skip-block devices do not
implement the block protocol, support was added to allow testing.

In addition, iochk was refactored into C++.

Change-Id: Id5ba1095b5aa8a8224b2608332adce60cbce73b3
Tested: Tested manually on astro and vim2.