While reading the docs, I saw a few typos, so I ran ispell through the
docs. Fixed:

- plain typos
- a few instances of 'ie'→'i.e.' and 'eg' → 'e.g.' for nicer style
- a few capitalisation issues (linux, unix)
- a few not-nice (IMHO) abbreviations (for a manual, that is):
  distro→distribution, repo→repository
- proper naming (RedHat→Red Hat)