sotruss: drop ksh support and add basic POSIX shell support

sotruss: drop ksh support and add basic POSIX shell support

This script works fine under bash as-is, so we don't need ksh anymore.

Once we tweak the function style, the code even works (for the most part)
under a POSIX shell.  The localized strings will be prepended with a $,
but it is otherwise functional.