add cm's modified mkbootimg dir/files

...

 On branch rz-4.3
 Changes to be committed:
	modified:   Android.mk
	modified:   bootimg.h
	modified:   mkbootimg.c
	new file:   unpackbootimg.c

Change-Id: Iff5aac8bd9810f8ea39d92fbec7e8224ca472be7