Unfortunately, I don't fully understand why it was leaking using the old
method of a lazy bytestring. I just know that it was leaking, despite
neither hGetUntilMetered nor byteStringPopper seeming to leak by
themselves.
The new method avoids the lazy bytestring, and simply reads chunks from the
handle and streams them out to the http socket.
Fixes the memory leak on store.. the second oldest open git-annex bug!
Only retrieve remains to be converted.
This commit was sponsored by Scott Robinson.
