Heritrix: Internet Archive Web Crawler

Allocation sites profiling showed a BDB util class
method, FastOutputStream.bump(), as a top garbage
creator (oftentimes, the top of all allocation sites).
Turns out that for our ~1K serialized CrawlURIs, a
buffer was being grown and copied to the larger version
multiple times per serialization.

Sleepycat reports others have runn into this and the
initial-size/grow will be better behaved and tunable in
BDBJE 2.0.

Slimming our CrawlURI serialization should help a lot
too. (See #1208747
http://sourceforge.net/tracker/index.php?func=detail&aid=1208747&group_id=7
3833&atid=539102
).

However, we can also refine SerialBinding slightly in
the meantime to reuse a single FastOutputStream per
thread, making the number of allocations here
negligible. (The single stream per thread would each
grow its buffer to a sufficiently spacious size
quickly, eliminating almost all initial allocations and
per-serialization grows.)