Reason: it was not able to deal with websites like amazon.com or
web.archive.org where links exist but responses are slow and time out.
Tried `--allow-timeout`, but didn't work.
- Fix unaccessible link to David Brackeen's tutorial
- Fix unaccessible link to Allegro 4.2 library
- Change description to Tricks of the Game Programming Gurus
- Add online library links to Tricks of the Game Programming Gurus
- Add More Tricks of the Game Programming Gurus
- Whitelist amazon.com due to 500 HTTP errors when site is still
available