remove AOSP su implementation

for our su

Change-Id: Ie1361cccacd172b0a22f559c646859ffe523a809
system_extras: Add make_ext4fs utility

Add make_ext4fs into $OUT/Utilities needed for some devices like Galaxy S I9000

Change-Id: Id9c9ce79282859542a1e44501b19594145d80275
ext4_utils: Yet another MMC discard pain in the ass

 * Secure discard on some devices are painfully slow.

Change-Id: Id6cc80ea7a25410b812803425a4b6267289834fb