changes in sbcl-1.4.5 relative to sbcl-1.4.4:
* minor incompatible change: building with/without the :sb-package-locks
feature is no longer an option. Package locks are always compiled in,
and removing :sb-package-locks from *features* will have no effect.
* enhancement: FIND-PACKAGE does not acquire a mutex
* enhancement: cheneygc can perform heap relocation on startup
* enhancement: in threaded builds, finalizers execute in a system-internal
thread so that a user thread which invokes GC is unblocked from performing
work as soon it returns from GC and invokes any post-GC hooks.
As such, it is more important than before to avoid assumptions about
special variable bindings in finalizers, even in single-threaded code.
* optimization: faster (funcall (or function symbol)) on x86-64.