genprimopcode: Replace LaTeX documentation syntax with Haddock

The LaTeX documentation generator does not seem to have been used for
quite some time, so the LaTeX-to-Haddock preprocessing step has become a
pointless complication that makes documenting the contents of GHC.Prim
needlessly difficult. This commit replaces the LaTeX syntax with the
Haddock it would have been converted into, anyway, though with an
additional distinction: it uses single quotes in places to instruct
Haddock to generate hyperlinks to bindings. This improves the quality of
the generated output.