mksh R59b

R59b is a must-have bugfix upgrade for R59:

• Handle other tmux $TERM types
• Fix typo in FAQ
• y='a\*b'; [[ $x = $y ]] regression fix
• Defuse CLIP OS O_MAYEXEC support
• Make set +o output a command to restore the currently set and (new!) cleared options, keep a reset state per session (experimental)
• Correct documentation and code regarding to argv[0] parsing: first - for login shells, then r case-insensitively for restricted shell, then sh*, again case-insensitively, for BINSH_* modes; add tests
• On OS/2, allow case-insensitive name for direct builtin call
• Always skip startup files if direct builtin call
• Avoid some sometimes-redundant startup codepaths