Cleanup for manual page.

Cleanup for manual page.

Rationale, major points:

- Esr's man-ext .SY macro is not portable.
  Even esr himself recommends to copy the implementation
  into the manual page itself if you *must* use it.
  But in the case at hand, it does almost nothing,
  so just use the portable .B instead.
- The glyph names \[char34] and \[char92] are not portable
  at all, but internal, undocumented groff features at best,
  and i'm surprised they work at all even with groff.
  Better use the portable \(dq and \e.

Rationale, minor points:

- The first .TH argument is by convention ALL CAPS.
- Use .PP and .sp as appropriate rather than blank lines.
- Drop useless .RS 0.
- New sentence, new line (sorry, that causes some churn).
- Some typos.

Thanks Ingo Schwarze for this patch.