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/functions.sh

@@ -392,7 +392,7 @@ function closure
 	done
 	return $r
 }
-closure 0 || err_exit -u2 'for loop function optimization bug2'
+closure 0 || err_exit 'for loop function optimization bug'
 dir=$tmp/dir
 mkdir $dir
 cd $dir || { err_exit "cd $dir failed"; exit 1; }