• make parsing numbers with leading digit-zero as octal independent of
mksh/lksh and dependent on set -o posix; adjust manpages to match
• warn about these changes and why mksh uses 32-bit consistent arithmetics
and point people to lksh for host-long undefined-behaviour arithmetics
• point out, explicitly, that it is *legal* for the operating environment
to make 'print $((2147483647 + 1))' (on a 32-bit system; adjust for a
64-bit system) to run 'rm -rf ~ /' instead
tg