In the process of making Mms unbundled, copy a few non-public-API
classes into the android-common library. The Mms app now uses this
library. The next step is to update the other apps that use these classes
and then delete the classes from their original location.
Have framework include the common source files directly when building,
then build common as a static library separately (depending on
framework, like everything else).
Goes with a companion change to build/core/pathmap.mk.
