Block size optimization - let rsync find the optimal blocksize by itself.

[tridge at samba.org]

> I believe that the compression option turns on compression of transfered
> data, including file lists, instruction streams etc. Even with compression
> turned off, the miss data in the delta is still compressed. 

nope!

Compression only compresses file data, not file lists etc. The file
lists are 'packed' with a simple fixed algorithm (finding common
filename prefixes for example). It would have been better to just use
deflate for the lot, but unfortunately I didn't do that.

If you don't use -z then deflate is not used at all, and neither is
the 'compression of unsent data' trick.

Cheers, Tridge