Upgrade to mksh R40.

Upgrade to mksh R40.

From the release notes...

R54 is a bugfix release with moderate new features:

[tg] Simplify and improve code and manual page
[tg] Try GCC 5’s new -malign-data=abi
[tg] Allow interrupting builtin cat even on fast devices (LP#1616692)
[tg] Update to Unicode 9.0.0
[Andreas Buschka] Correct English spelling
[tg] Handle set -e-related error propagation in || and && constructs correctly
[tg] Initialise memory for RNG even when not targeting Valgrind
[tg] Shrink binary size
[Brian Callahan] Improve support for the contemporary pcc compiler
[tg] Fix side effects with lazy evaluation; spotted by ormaaj
[tg] New flags -c (columnise), -l, -N for the print builtin
[Larry Hynes] Fix English, spelling mistakes, typos in the manpage
[tg, ormaah] Return 128+SIGALRM if read -t times out, like GNU bash
[Martijn Dekker] Install both manpages from Build.sh
[Martijn Dekker] Document case changes are ASCII-only
[Ronald G. Minnich, Elbing Miss, Álvaro Jurado, tg] Begin porting to Harvey-OS and APEX (similar to Plan 9 and APE)
[KO Myung-Hun] More infrastructure for the OS/2 (EMX, KLIBC) port

I've continued to disable the cat, realpath, and sleep builtins,
and added print to the list (now I've realized it's unrelated to
the print on the desktop).

Bug: N/A
Test: manual
Change-Id: Iead4c1b572c6f288b2ab2b884125dcb606f1e356