swift234

change LValue from holding its segments as a DiverseList to holding them
as a std::vector<std::unique_ptr<PathComponent>>.   DiverseList memcpy's
around its buffer on copy and move operations.  This seems safe with all
of the current implementations of Cleanup, but is absolutely not with the
LValue PathComponents.  These things hold std::vectors, RValue (which has
an std::vector in it), and a bunch of other probably non-trivial things.

While we're in here, disable the copy constructor, since it isn't safe.
This doesn't harm mainline, but was burning me on a patch I'm working on.

When/if someone cares about performance optimizing this code, a better
approach would be to use an ilist + bump pointer allocator.



Swift SVN r21057