Merge branch '2.4.x'

* 2.4.x:
  utils/str.3: Fix typeface for mathematics.
  sys/tests.at: Add full stops after header comments.
  codec/codec.3: Fix spacing after ellipsis.
  utils/t/bits-testgen.py: Set the `SEED' from the command-line correctly.
  utils/t/bits-testgen.py: Make `arg' return arguments in the right order.