of a local varnum (lvarnum) in each allocator.
* src/misc/bddalloc.cc (bdd_allocator::bdd_allocator): Initialize
lvarnum.
(bdd_allocator::extvarnum): New method.
(bdd_allocator::allocate_variables): Use lvarnum and extvarnum.
* src/misc/bddalloc.hh (bdd_allocator::extvarnum): New mathod.
(bdd_allocator::lvarnum): New variable.