Squashed 'app/jni/hole_punch/' content from commit 69ea832

git-subtree-dir: app/jni/hole_punch
git-subtree-split: 69ea832fc27d89d7283d9be17c67fa68db41ad20
Merge commit '6d84124d625fb85d0ceba889f9545674bd6ce73a' as 'app/jni/hole_punch'
Add initial Android native library for NAT hole puncher
Fix incorrect package for RemoteApiServiceTest
Add MGClient and its test code
Pre-populate armeabi directories

For unknown reason, armeabi directories need to be pre-populated when
building native libraries.