manual: miscellaneous improvements
manual: miscellaneous improvements

- use a roman font for comments in the TeX outputs.
- fix some typos and missing @lispcmt{}s.
- insert page breaks before each CLHS-style documentation node.
  This should make it much clearer to read and browse, at the
  expense 23 more pages in total, a ~25% increase.

cffi/cffi,wesen/cffi,wesen/cffi,mcna/cffi,3b/cffi,marsijanin/cffi,3b/cffi,attila-lendvai/cffi,3b/cffi,marsijanin/cffi,stassats/cffi,wesen/cffi,dochang/cffi,dkochmanski/cffi,akovalenko/cffi,dochang/cffi,akovalenko/cffi,stassats/cffi,cffi/cffi,kingcheez/cffi-cheez,dkochmanski/cffi,stassats/cffi,kingcheez/cffi-cheez,kingcheez/cffi-cheez,cffi/cffi,mcna/cffi,marsijanin/cffi,dkochmanski/cffi,attila-lendvai/cffi,dochang/cffi,akovalenko/cffi