Extremely basic integration of wvtest for testing.

And move test scripts into t/ subdir to keep things clean.

As part of that, make sure redo adds itself to the PATH on startup so that
subscripts can find it.

hello.c

@@ -1,7 +0,0 @@
-#include <stdio.h>
-
-int main()
-{
-    printf("hello, world!\n");
-    return 0;
-}