bdd_uniquecomp, bdd_appexcomp, bdd_appallcomp,
bdd_appunicomp): Declare for C and C++.
* src/bddop.c (CACHEID_EXISTC, CACHEID_FORALLC,
CACHEID_UNIQUEC, CACHEID_APPEXC, CACHEID_APPALC,
CACHEID_APPUNCC): New macros.
(quatvarsetcomp): New variables.
(varset2vartable): Take a second argument to indicate negation,
set quatvarsetcomp.
(INVARSET): Honor quatvarsetcomp.
(quantify): New function, extracted from bdd_exist, bdd_forall,
and bdd_appunicomp.
(bdd_exist, bdd_forall, bdd_appunicomp): Use quantify.
(bdd_existcomp, bdd_forallcomp, bdd_appunicompcomp): New functions.
(appquantify): New function, extracted from bdd_appex, bdd_appall,
and bdd_appuni.
(bdd_appex, bdd_appall, bdd_appuni): Use appquantify.
(bdd_appexcomp, bdd_appallcomp, bdd_appunicomp): New functions.

* src/bddop.c (bdd_support): Return bddtrue when the support
is empty, because variable sets are conjunctions.