Various markup fixes in doc
Various markup fixes in doc

This fixes sphinx warnings and fixes some weird-looking markup.

Signed-off-by: Etienne Millon <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@emillon.org>

janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder