[zx][rights] Test object traits

This also fixes some bugs. Logs are actually user signalable. And
vmars cannot be waited on, and thus should not have the RIGHT_WAIT.

Change-Id: I2b560ef56ef3367cd7959f35e03791aece329da2

[zx][fzl] Implement ticks class, fzl helper library.

This patch:
- Implements the zx::ticks class, wrapping zx_ticks_t
- Implements the fzl library, which provides a C and C++ API
for converting between nanoseconds and ticks. Since libzx is
intended to act purely as a C++ wrapper class around the underlying
C API, fzl contains "more-complex-than-just-syscall" logic for general
Zircon-specific system helpers.
- Tests both changes.

Change-Id: I089e3cd64b780042d1cb7a48e455a10e21b2cf20

[utest][zx] Fix an mx->zx straggler

Change-Id: I59862c44e2a6304860fe659d063abb79d41950b1

[zx] Rename libmx test to libxz, mxr-mutex test to zxr-mutex

The Lesser Renaming is here!

Change-Id: I67a24e0ac9baa888e3fd08c97a22d76d17e3bf56