[Brillo] Add XmlRpc++ library

Adding a third-party native XML RPC library for Shill testing on Brillo.

Bug: 24335496
TEST: source build/envsetup.sh && lunch aosp_shamu-userdebug && 
make -j 64

Change-Id: I7a4d86fc3ab3b85f981e1814c1ef44eab85471b5
67 files changed