mksh R59c

R59c bundles tons of bug and portability fixes:

• Update character widths (Jamo bugfix)
• Don’t use test -e in Build.sh
• Mac OSX-specific: ensure ulimit -m is present even if it is an alias of ulimit -v (10.4+), for compatibility
• Port to A/UX
• Add older ulimit(2) support, if setrlimit(2) is missing
• More EBCDIC-safeness (slightly…)
• Allow all tests to pass with very old Perl 5
• Fix test.sh’s output of tested/expected shell version
• Let A/UX default CC to gcc
• Drop “is being ported” warning from A/UX and OS/2, they work
• Include <pwd.h> only if MKSH_NOPWNAM is not defined
• command -v must print absolute pathnames, even if $PATH contains relative pathnames under which the command in question was found
• Fix absolute pathnames relative to / on nōn-OS/2, too
• Fix some more corner cases related to pathname normalisation
• FAQ: ${@?}: bad substitution documentation
• Fix some constructs pointed out by https://www.deepcode.ai/
• Clean, refactor, optimise some code
• Allow ^Xe on empty command line; quote editor argument properly
• FAQ: an IRC user suggests ^Xe for ad-hōc scripts and multiline
• Eliminate many unnecessary calls to (re‑)allocate memory
• Correct order during tree-printing of heredocs
• Drop some possibly unreached and probably broken code
• Increase FAQ2HTML.sh compatibility with pre-POSIX shells
• Demote some (unlikely called) output code to !MKSH_SMALL