Merge changes from topic "pppolac"

* changes:
  pppd: Convert Android.mk to Android.bp
  pppd: Add rules for building the pppol2tp-android plugin
  pppd: Fix pppol2tp-android.so build
  pppd: Enable plugin support in pppd
  pppd: Add pppol2tp-android plugin
  pppd: Remove obsolete way of receiving args from mtpd
tree: 0b26260efce8da808ad742b0545f41adae2fcb73
  1. pppd/
  2. Android.bp
  3. CleanSpec.mk
  4. README.version