[SQLObject] Cache Lock Problems

(Using SQLObject 0.3-CVS)
Hello all -

Wow. Had a big long email written out, went back to debug a
little more after lunch, and found the bug(s). Still would
like a way to _completely_ turn off caching, including
weakref\'ing. But it'd only be useful for us on days like
today, when we're suffering from a bug there and would
prefer to have all but one of us just avoid it. :)

Symptoms: We've been having SQLObject completely hang the
python interpreter on a regular basis, after some digging
it turned out to be during Cache lookups. More
specifically, if you stored an object, then destroyed it
(purge in Cache), then tried to do a lookup for that id in
the cache again (expecting failure), it would hang. Having
found the problem, it's likely this behavior could happen
at other points, but that's the easy way to duplicate. :)

Fix: Cache.py is missing a lot of lock statements. I've
attached a fixed version with "## LDO" comments, they are
all in get() or put().

- Luke