t/*: rearrange tests into numbered directories.

It was getting way too ad-hoc in there.  Let's reorganize the tests so that
there's a good, obvious, suggested sequence to run them in.

t/250-makedir/autosubdir/all.do

@@ -0,0 +1,3 @@
+rm -rf sub.tmp
+redo-ifchange sub.tmp/test.txt
+[ -e sub.tmp/test.txt ] || exit 96

t/250-makedir/autosubdir/clean.do

@@ -0,0 +1,2 @@
+rm -rf *.tmp
+rm -f *~ .*~

t/250-makedir/autosubdir/default.txt.do

@@ -0,0 +1,2 @@
+mkdir -p $(dirname $1)
+echo "hello" >$3