buildroot.html: html code clean-up and other issues - Part2

The current DocType declaration was incorrect. It is neither xhtml strict nor
xhtml transitional. So, instead of dealing with that issue, converted it to
validated Html5.

Fixed white-space errors.
Removed validator html4.01 code.
Color corrected the code sections.
Removed redundant or useless html code.
Changed foo to libfoo, for consistency.
Changed page bookmarking to use header id's.
Re-flowed paragraphs to line break at 80 characters.
Re-formatted the code sections for consistency and correctness.
Kept all list items, headings, and href's on a single line (where possible).

Signed-off-by: Martin Banky <Martin.Banky@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>