Strip whitespace-at-eol from documentation
Fix a number of typos in the documentation

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)
Merge pull request #2018 from iustin/master

A few documentation fixes
Revert "Print a more friendly message when http_proxy is down."

This reverts commit 03c134d5d7d65ce8bb019bc28657fbd6cc9cc999.

Committed by mistake.
Run 'regenerateHaddockIndex' when we're in a sandbox.

Fixes #1337.
Tweak the code a bit.
Hoist the 'forRepl' check out of 'whenVanillaLib' & friends.

Makes it more clear what is going on.

Fixes #1715.
Formatting.
Don't build shared/prof objects from C sources in repl mode.
bootstrap.sh: install profiling and shared libs.

Fixes #2009.
Fix the 'cabal.exe' link.