Allocate 1 GB because we need this to compile Base.oz.
Fixed bug in IsFuture and Value.status for ReadOnlyVariables.
Added some rudimentary dump() methods for threads.
Fixed a bug that could create cyclic References.

E.g. when trying to unify A and B whilst both refer to the same
store node.
Fixed: forgot NamedName and UniqueName in LiteralLike and NameLike.
Changed the opcode condBranch. Now supports backward branches.

Instead of having 3 arguments (false, true and error branches),
now it has only 2 arguments (false and error branches). If the
arbiter is true, no branching is made.

The opcode has 4 alternatives, depending on whether the false
and error branches are backward or not.