* If the basename of argv[0] starts with "sh", activate FPOSIX early,
preventing some typical ksh aliases from being defined.
* If FPOSIX, don't pre-define aliases (except integer and local) to
benefit operating environments that never heard of the great Korn Shell.
* Support x=(a b c) bash-like array initialisation
* Support ${foo:2:3} bash-like substring expansion
* Don't try to execute ELF, a.out, COFF, gzip or MZ binaries, e.g.
mksh /bin/sh.
* Prefer well-known signal names to alphabetically earlier ones
* Fix a bug delivering ERR and EXIT pseudo-signals to traps combined
with "set -e".
Update from mirabilos#pkgsrc with small fixups by me.
096522cddc