Following Google's lead, we now package two jars. The v4 jar contains
classes that are compatible back to API level 4 (Donut / 1.6). The
v13 jar includes all the v4 classes as well as some that require API
Level 13 (Honeycomb MR2 / 3.2). To see what's new in ACL r4, view
Google's release notes here:
http://developer.android.com/sdk/compatibility-library.html