for modules starting with the __dirname and moving up.

This makes it much easier to localize dependencies to a particular program.

This way, the "default" paths of ~/.node_libraries and {prefix}/lib/node are only checked *after* anything that the user has placed into the NODE_PATHS environ, or pushed onto require.paths.

This makes require.paths a much more effective write-target, albeit slightly less useful as a read-target.  However, given the existence of require.resolve(), this is less of an issue -- if you want to know what a module ID will map to, just ask that question and get an authoritative answer from the loading machinery.

Also, hack the repl so that it works as expected there, too.

Mostly just upgraded tools/test.py to the latest one that's in V8.  But also
fixing the before and after hooks to preserve the test/tmp directory so that
running tests manually usually works.

Originally written to try to track down this bug report:
http://permalink.gmane.org/gmane.comp.lang.javascript.nodejs/13924

As it turns out, it's showing a completely different kind of failure.  When
the file is base64 encoded with the native program, then decoded with node,
it doesn't match the original.  Something's fishy.

Add SIGTERM and SIGINT signal handlers so that we run the exit handlers
before exiting when getting these signals. Fixes an issue where we
couldn't run vi after CTRL+C'ing node because the stdin fd was left
non-blocking.

needs tests (particularly for pipeline situations)