* update references in `--cc` flag, using modern gcc examples
* note that issues should not be filed if `--cc` flag is used
* remove reference to `HOMEBREW_CC` as it should not be exposed to users
* generate manpages using `brew man` with these changes
GitHub now nicely generates a documentation site for us at
http://brew.sh/brew based on our docs folder. Optimise the output of
this and the GitHub docs directory for readability and the various user
groupings.