fix even more broken markdown links

Added `bin/find-missing-links.sh` tool to check for
markdown links to missing local files.

Regarding the missing link tool:

```
    Here be extended regular expression magic dragons! :-)
```

Added `make find_missing_links` to the top level Makefile.

Added `make find_missing_links` to `make www` and `make quick_www`.

Ran `make www` to perform the above.

TODO: Fix markdown links to missing local files.

2011/eastman/README.md

@@ -48,7 +48,7 @@ aren't familiar with it. Back in its day, this demo inspired lust and awe in
 geeks around the world.
 
 The graphics are
-[raytraced](https://en.wikipedia.org/wiki/Ray_tracing_(graphics), with
+[raytraced](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)), with
 procedural textures on the ball and the back wall.  I did cheat a little to
 simplify the calculations: it uses a parallel projection, but textures the back
 wall to look as if there were a floor being viewed in perspective.  The shadow

2011/eastman/index.html

@@ -421,7 +421,7 @@ the Commodore Amiga. See <a href="https://www.youtube.com/watch?v=-ga41edXw3A" c
 aren’t familiar with it. Back in its day, this demo inspired lust and awe in
 geeks around the world.</p>
 <p>The graphics are
-[raytraced](https://en.wikipedia.org/wiki/Ray_tracing_(graphics), with
+<a href="https://en.wikipedia.org/wiki/Ray_tracing_(graphics)">raytraced</a>, with
 procedural textures on the ball and the back wall. I did cheat a little to
 simplify the calculations: it uses a parallel projection, but textures the back
 wall to look as if there were a floor being viewed in perspective. The shadow