update Hh_prelude to match recent version of Core_kernel
Summary:
I recently tried to update to a more recent ocaml/core_kernel and got
bitten by the polymorphic equal. Recent versions of Core_kernel restrict = to
be Int.equal, and explicit use of Poly.equal for polymorphic occurences.
This diff replace the actual ban of polymorphic equality with Int.equal.
Replacing `open Core_kernel` with `open Hh_prelude` will allow me to
replace lots of the current polymorphic equal (see next diff in stack for
an example)
Reviewed By: andrewjkennedy
Differential Revision:
D20940202
fbshipit-source-id:
3e0fde06aa4e6448badb524cf6495be526b685f1