Add linux unused code tracking

Track various large hunks which have been dropped simply
because they are not relevant to this port.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

lib/libzfs/include/libzfs.h

@@ -643,15 +643,6 @@ extern int zfs_unshareall(zfs_handle_t *);
 extern int zfs_deleg_share_nfs(libzfs_handle_t *, char *, char *, char *,
     void *, void *, int, zfs_share_op_t);
 
-/*
- * When dealing with nvlists, verify() is extremely useful
- */
-#ifdef NDEBUG
-#define	verify(EX)	((void)(EX))
-#else
-#define	verify(EX)	assert(EX)
-#endif
-
 /*
  * Utility function to convert a number to a human-readable form.
  */