memoisation on r_equal too.

nsl went from 12s to 11.1s
1 job for hashcons in 10 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #4406
build

00:00:10

 
Name Stage Failure
failed
build Test
ocamlfind ocamlopt -c -g -bin-annot -package fmt.tty -package fmt -package ANSITerminal -I src -o src/side.cmx src/side.ml
ocamlfind ocamlopt -c -g -bin-annot -package fmt.tty -package fmt -package ANSITerminal -I src -o src/term.cmx src/term.ml
+ ocamlfind ocamlopt -c -g -bin-annot -package fmt.tty -package fmt -package ANSITerminal -I src -o src/term.cmx src/term.ml
File "src/term.ml", line 1291, characters 14-29:
Error: Unbound module Memoisation
Command exited with code 2.
Makefile:9 : la recette pour la cible « native » a échouée
make: *** [native] Erreur 10
ERROR: Job failed: exit status 1