[MERGE] Implement bzrlib.lock with CreateFile rather than LockFileEx on win32 (operational part)

[Martin (gzlist)]

Here is the patch (attached lock_on_create.bundle) as discussed in the
preceding RFC thread. The motivation for change is better
compatibility and slightly simpler code. It follows the current design
and naming, so it is clear from the diff what exactly is being
changed. However it keeps, notably: existing limitations, duplication
of code, various redundancies - especially with win32utils, and does
not add to the sparse documentation.

I welcome feedback on the larger design questions for a followup
patch, but would like to see this version merged promptly so there can
be some testing on a wider range of windows systems, and in a full
range of scenarios involving plugins and so on.

Martin
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