Changes present in rt45632 were applied as two separate commits:

  - documentation cleanups and proper handling of -4/-6 in delv and mdig
    (applied to v9_9, v9_10, v9_11 and master); the commit in v9_9 has a
    bit different CHANGES entry and commit log message as 9.9 contains
    neither delv nor mdig as officially distributed tools and thus the
    commit boiled down to documentation fixes,

  - adding -4/-6 to nsupdate and rndc (only applied to master).