Seems that locking of annexed objects when they're being dropped was broken
in direct mode:
* When taking the lock before dropping, it created the .git/annex/objects
file, as an empty file. It seems that the dropping code deleted that,
but that is not right, and for all I know could in some situation cause
a corrupted object to leak out.
* When the lock was checked, it actually tried to open each direct mode
file, and checked if it was locked. Not the same lock used above, and
could also fail if some consumer of the file locked it.
Fixed this, and added windows support by switching direct mode to lock a
.lck file.
transferkeys had used special FDs for communication, but that would be
quite annoying to do in Windows.
Instead, use stdin and stdout. But, to avoid commands like rsync stomping
on them and messing up the communications channel, they're duplicated to a
different handle; stdin is replaced with a null handle, and stdout is
replaced with a copy of stderr. This should all work in windows too.
Stopping in progress transfers may work on windows.. if the types unify
anyway. ;) May need some more porting.
