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/101-atime/.gitignore

@@ -0,0 +1 @@
+atime2

t/101-atime/all.do

@@ -0,0 +1 @@
+redo atime

t/101-atime/atime.do

@@ -0,0 +1 @@
+redo atime2

t/101-atime/atime2.do

@@ -0,0 +1,6 @@
+# make sure redo doesn't think merely *reading* the old file counts as
+# modifying it in-place.
+cat $1 >/dev/null 2>/dev/null || true
+./tick
+cat $1 >/dev/null 2>/dev/null || true
+echo hello

t/101-atime/clean.do

@@ -0,0 +1 @@
+rm -f atime2 *~ .*~

t/101-atime/tick

@@ -0,0 +1,6 @@
+#!/usr/bin/env python
+import time
+
+t1 = int(time.time())
+while int(time.time()) == t1:
+    pass