[MERGE] remerge command works on win32

[Aaron Bentley]

Martin Pool wrote:

>>I can change this, sure.  We may get more errors on Win32, but those 
>>errors would have manifested on the next merge/revert command anyhow.
> 
> 
> I can understand that.  But remember that exceptions here don't just
> mean "I failed to cleanup the limbo directory" in the usual sense, but
> also "there's a programming error in the cleanup code" or "the user hit
> C-c during cleanup"; in both those cases we should terminate.  I'd
> prefer to catch the IOErrors in fairly restricted scopes and report them
> with a warning.

Perhaps we should catch IOErrors.  I would be fine with not catching
anything.

Aaron