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/example/main.c

@@ -1,8 +0,0 @@
-#include <stdio.h>
-#include "mystr.h"
-
-int main()
-{
-    printf("%s\n", mystr);
-    return 0;
-}