ext4_utils: add filesystem capabilities support.

Add support for specifying filesystem capabilities when
creating a new filesystem.

The combination of SELinux extended attributes plus
filesystem capability extended attributes is too big
to fit inside one inode entry. Because of this, I added
support to ext4_utils to create an xattr block and link
the inode to that block. We continue to try to fit
everything inside the inode if possible, but fall over to
creating a block if the extended attribute is too big.

Change-Id: I40ebb63975b15ecd8c565486e171b4d50cd4dfaa
diff --git a/ext4_utils/ext4_utils.c b/ext4_utils/ext4_utils.c
index 4b87c6e..c3bec96 100644
--- a/ext4_utils/ext4_utils.c
+++ b/ext4_utils/ext4_utils.c
@@ -126,6 +126,7 @@
 	aux_info.bg_desc = calloc(info.block_size, aux_info.bg_desc_blocks);
 	if (!aux_info.bg_desc)
 		critical_error_errno("calloc");
+	aux_info.xattrs = NULL;
 }
 
 void ext4_free_fs_aux_info()