ext4: Add EXT4_IOC_MIGRATE ioctl

The below patch add ioctl for migrating ext3 indirect block mapped inode
to ext4 extent mapped inode.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

diff --cc fs/ext4/Makefile
Simple merge

diff --cc fs/ext4/extents.c
Simple merge

diff --cc fs/ext4/ioctl.c
Simple merge

diff --cc fs/ext4/migrate.c
Simple merge

diff --cc include/linux/ext4_fs.h
Simple merge

diff --cc include/linux/ext4_fs_extents.h
Simple merge