[merge] Implement put_bytes_non_atomic for smart server

[John Arbash Meinel]

The attached patch adds 'put_bytes_non_atomic' for the smart server.
This allows us to avoid a bunch of round trips when creating new
directories on the remote end. This is only really a win for pushing a
new project, since once a project is established we rarely get many
remote directories that need to be updated.

For a small branch (a plugin of mine with 29 revisions), over sftp and
the same 35ms latency, 30KB/s up, 160KB/s down:

sftp		21-30s
bzr.dev		10-14s
put-nonatomic	9-13s

This isn't as big of a win as the readv() changes. It only saves a few
round trips (at most 256*2, one for the failed put, and one for the
mkdir for each new directory)

Now, this will have bigger benefits for projects with larger changes,
since the SmartServer's put() command involves sending all of the data.

So if we fail to create a .knit file, we have to send all of that data a
second time.

The times for pushing all of bzr.dev look like this:

sftp		21:12.59
bzr.dev		21:11.32
put-nonatomic	20:21.43
bzr-0.10 sftp	25:15.25

These take long enough, that I only ran each one a single time. One good
thing is to see that the put_non_atomic code and other knit fixes really
will make bzr-0.11 quite a bit faster than 0.10 over any protocol.

By the way, there seems to be a bug in the protocol when there is a ','
in the path. I originally tried to push to 'bzr://host:port/,tmp' and it
kept telling me:

 Path
'bzr://phoenician.i-clic.uihc.uiowa.edu:9999/,tmp/test-version-info/' is
not a child of path 'bzr://phoenician.i-clic.uihc.uiowa.edu:9999/%2Ctmp/'

So something is using an unescaped url, and something else is using the
escaped form, and .relpath() is being called.

So this isn't as big a win, but I still think it is useful.

Oh, and it is important to note that pushing a bzr.dev tree moves about
40MB of data, and 40MB / 20min ~= 33KB/s. So it seems to be completely
maxing out my upload capacity, which is a good sign.

John
=:->
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