Create an UnwindMapLocal object.

The way libunwind handles local unwinds is different from remote unwinds,
so create a new map object to handle the differences.

Add new test to verify the map data is being generated correctly.

Add new tests to check for leaks.

Refactor the BACK_LOGW code into a single header file.

Change-Id: I01f3cbfc4b927646174ea1b614fa25d23b9b3427