Added fuzzer for Unwinder

Adds a fuzzer for Unwinder. This will likely cover a large portion of the library, as it uses many of the library's features
in the process of setting up the Unwinder. Hopefully this, combined with the calls Unwinder makes internally, will provide
sufficient coverage.

Rough coverage estimate (this is drastically lower than the true number due to shared libraries): 6.6%

Test: Ran on device for a few hours
Signed-off-by: Dylan Katz <dylan.katz@leviathansecurity.com>
Change-Id: I813e204df595ff38dccfb73be7fff5c080aaa043