Backport ksh93v- regression tests and fix various regression test bugs (#472)

- tests/*.sh: Backported many additional regression tests and test
  fixes from the alpha and beta releases of ksh93v-.

- tests/alias.sh: Avoid trying to add vi to the hash table, as some
  platforms do not provide a vi(1) implementation installed as part
  of the default system. This fixes a regression test failure I was
  getting in one of my Linux virtual machines.

- tests/builtins.sh: Fixed a bug in one of the regression tests that
  caused an incorrect total error count if any of the tests failed.

- tests/sh_match.sh: Fixed a regression test failure on DragonFly
  BSD caused by the diff command printing an extra 'No differences
  encountered' line.

src/cmd/ksh93/tests/substring.sh

@@ -306,7 +306,7 @@ done
 
 (
 PS4=$tmpPS4
-[[ $(string=$string $SHELL -c  ": \${string/$pattern/}; print \${.sh.match[26]}") == Z ]] || err_exit -u2 'sh.match[26] not Z'
+[[ $(string=$string $SHELL -c  ": \${string/$pattern/}; print \${.sh.match[26]}") == Z ]] || err_exit 'sh.match[26] not Z'
 : ${string/$pattern/}
 (( ${#.sh.match[@]} == 53 )) || err_exit '.sh.match has wrong number of elements'
 [[ ${.sh.match[@]:2:4} == 'B C D E'  ]] || err_exit '${.sh.match[@]:2:4} incorrect'