Univ: an attempt to lazily compact chains of Equiv in a functionnal way
Univ: an attempt to lazily compact chains of Equiv in a functionnal way

 We'll see experimentally if this helps... A few more functions could
 be adapted (e.g. between), and an occurence of compare just discard
 the compacted graph (in compare_greater)

git-svn-id: 44dc50bdcc0f5d1a212c497508dc9452e0b35e2b@13723 85f007b7-540e-0410-9357-904b9bb8a0f7

maximedenes/native-coq,maximedenes/native-coq,maximedenes/native-coq