Normally, creating the target $1 yourself is bad; create $3 instead. But if
$1 is a directory, we'll allow it. That way 'redo subdir' can call
subdir.do, and subdir.do can both create the directory *and* run a bunch of
sub-.do files on it.
Now 'redo test' runs the tests, but 'redo t' just builds the programs.
Also removed wvtest stuff; we're not really using it properly anyway and
it's not helping our testing right now. It might come back later.
