Add LOCAL_APK_LIBRARIES argument.

This allows you to build apks that link against other
apks using the framework's new shared library apk feature.

Also if you are using LOCAL_APK_LIBRARIES, then LOCAL_DEX_PREOPT
will not be allowed.  This is because using preopt means the
apk is stripped of its dex file, so the pre-installed apk can't
be redexed if its associated library changes.  (Even if the build
system didn't strip the dex, Dalvik still has issues because it
assumes a pre-odex file is always valid.)

Change-Id: I952c0d24f8975f75aff67f78b5faeec91144c3e7