put mksh in the cross-shell-tests

TODO

@@ -1,111 +0,0 @@
-Things I want
-=============
-
-Molly guard
--------------
-The Molly-guard should be more accepting so that people don't have to use it
-all the time and thus get used to using it. For example, you shouldn't need to
-pass -f in this case.
-https://github.com/creationix/nvm/issues/357
-
-Test speed
--------------
-Make tests run faster.
-https://github.com/bike-barn/hermit/issues/62
-
-First, easier thing is probably to run tests in parallel.
-
-Second, also easier thing is to tell people to save things to RAM rather than
-disk whenever they can.
-
-Third, harder thing is to put the test suite in RAM automatically. Maybe the
-whole test directory, which includes fixtures, gets copied to a tmpfs if one
-exists.
-
-Hmm or maybe there's a compromise: Tell people to mount /tmp as a tmpfs so
-that temp files are fast. Maybe allow people to set some other directory as
-the temporary file place, in case they want a different tmpfs location.
-
-Options
--------------
-I want long options. For example, there's presently -f and -e.
-I want to make them -f|--force and -e|--exit.
-
-Environment variables
--------------
-Do something to make it easier to debug environment variables, because that is
-often confusing.
-https://github.com/creationix/nvm/issues/719
-https://github.com/creationix/nvm/issues/589
-
-Documenting that people should run "env" when their tests fail might be good
-enough.
-
-Licensing and copyright
-------------------------
-* Reference all owners and years in the Copyright file
-* Consider copyleft licenses
-* Add license notices to other files if necessary
-
-Packaging
-------------
-Package for package managers.
-
-* I want NixOS, of course.
-* Debian is probably the big one.
-
-Other interesting package managers
-
-* Update the npm package
-* Homebrew (for Mac)
-
-Windows
-----------
-Try running Urchin in Windows somehow. Interpreters include
-
-* CygWin (https://www.cygwin.com/)
-* MSYS (http://mingw.org/wiki/msys)
-* GNU on Windows (https://github.com/bmatzelle/gow/wiki)
-* Git for Windows (https://git-scm.com/download/win)
-* win-bash (http://win-bash.sourceforge.net/)
-
-Consider copyleft licenses
-----------
-ScraperWiki owns the original version of Urchin (Thomas Levine did the early
-work as part of his work for ScraperWiki.) and originally licensed it under an
-MIT-style license. Other people made changes after this original ScraperWiki
-version. As of January 2016, they are just Thomas Levine (when he wasn't
-working for ScraperWiki) and Michael Klement.
-
-The original license was MIT just because that's what ScraperWiki put on
-everything. Should we change the license?
-
-The MIT-style license grants pretty much all rights. It says that you need
-to attribute when you redistribute source code, but you don't
-necessarily have to redistribute source code.
-
-A copyleft license adds the restriction that modified versions of the
-code need to be licensed under the same license. GNU licenses in
-particular require that source code be released if non-source versions are
-released, and the different GNU licenses differ in what how the
-non-source version is defined. (The original, GPL, discusses compiled
-binaries.) Copyleft doesn't mean anything specific for commercial use.
-
-MIT-licensed code can be modified and then licensed as GPL, because MIT
-license allows that, but GPL code can't be modified as MIT, because MIT
-doesn't allow that. And if we get all of the authors to agree on it, we
-can always add whatever crazy license we want, regardless of what we
-have already.
-
-The distinction between MIT-style and GNU-something might matter quite little
-in the case of Urchin.
-
-1. Urchin is written in an interpreted language (shell), so it might be
-   hard to distribute usefully without providing the source code.
-2. Urchin just runs tests; it doesn't get compiled with the rest of the
-   code (also because it's in shell). Thus, I think a GPL license on
-   Urchin wouldn't infect the code being tested.
-
-This is as far as I have gotten with contemplating license changes. For now
-we're sticking with the original MIT-style license, but it's easy to change
-licenses later.

cross-shell-tests

@@ -2,7 +2,7 @@
 # Run urchin in a bunch of different shells,
 # including a shell that isn't quite POSIX-compatible (zsh)
 
-for shell in dash bash ksh zsh; do
+for shell in dash bash mksh ksh zsh; do
   if which $shell > /dev/null 2> /dev/null; then
     echo
     echo Running urchin tests in $shell