add option to make_ext4fs to record blocks for each file

Add the -B option to make_ext4fs, which causes it to record the block
ranges used for each (regular) file in the image.  We can use this
information to construct more efficient block-based incremental OTAs.

Bug: 16984795
Change-Id: I2a5325bb89948f63c76e93fdfa84c51f9b050104
diff --git a/ext4_utils/extent.c b/ext4_utils/extent.c
index abb30ce..7142c8b 100644
--- a/ext4_utils/extent.c
+++ b/ext4_utils/extent.c
@@ -202,7 +202,7 @@
 
 /* Allocates enough blocks to hold len bytes, queues them to be written
    from a file, and connects them to an inode. */
-void inode_allocate_file_extents(struct ext4_inode *inode, u64 len,
+struct block_allocation* inode_allocate_file_extents(struct ext4_inode *inode, u64 len,
 	const char *filename)
 {
 	struct block_allocation *alloc;
@@ -214,8 +214,7 @@
 	}
 
 	extent_create_backing_file(alloc, len, filename);
-
-	free_alloc(alloc);
+    return alloc;
 }
 
 /* Allocates enough blocks to hold len bytes and connects them to an inode */