Remove the warning that recommends setting --infer when %inline is used.

after a change in the wording of the warning:
"1 production is never reduced".

(These options are not yet implemented.)

Documentation: document the use of ocamlbuild.
The upcoming interaction with dune is not yet documented.

Html rendering of the manual

See merge request !4

  https://github.com/maranget/hevea/blob/d483550/hevea.sty

The macros in sigplanconf.hva seem enough to build main.tex as it
exists today.

In theory, the two are not quite equivalent when surrounded by
whitespace. In practice, I didn't see a difference.

(Makes no difference in practice, because formal parameters
are already renamed elsewhere (PartialGrammar) and can never
conflict with toplevel symbols.)