File download retries...

Ugh. So, some servers really suck and claim they don't have some file--BUT
THEY REALLY DO! I will never understand this, so, as a hack, we will retry
the same file up to three times. To prevent this from being a
spin-error-boom loop a phailure, we'll retry files at the very end of the
patch proc.

See also:
http://www.mystonline.com/forums/viewtopic.php?p=408060#p408060
Reorganize pfPatcherStream memory management...

... I think this is slightly more sane?
Chunk-average DL speeds...

... The previous code did file-average speeds, which were pretty lame for
big files. This is probably equally lame, but in different ways. At least
in doesn't tell you you're downloading at 24 KiB/s and the progress bar is
zooming.
HACK: More useful patcher error message.

This is somewhat hacky, but we need to have a better error message on
patch fail. This fits the bill, except, once again, there is no
localization. Sigh.