- Same googletest release (v1.8.0), new root in third_party.
- Update Android.mk and make build (include and file locations).
- Update cmake build (use googletest's cmake support).
- Update gtest include in all tests.

BUG=https://bugs.chromium.org/p/aomedia/issues/detail?id=76

Change-Id: I5491a2ff3c8869263cd885872c815402236c20b1