Over 2 months late -- this is how much I procrastinate. -_-

Fixes issue https://github.com/ry/node/issues/issue/481

It's symlinked to /usr/bin so this test fails.

This reverts commit 97970b05.

It looks like MINGW doesn't like to write() to sockets.
If wrong, revert this patch

When clearTimeouts was called on a timer multiple times, it would break the
doubly-linked list along with future timeouts. This patch fixes that.

This code is functionally equivalent, but in a simpler form.  Now new
parameters to `execFile` do not require `exec` to be refactored.

Originally added in commit 078a48a9, this code dealt with an optional
env parameter that was passed to `exec`.  The parameter was removed, but
this code was left.  As it serves no purpose, removing it.