Release 2.5.1
Start development series 2.5.1-post
When reusing Curl connections, reset timevalue and maxfilesizelarge
Cope with unresponsive PackageKit
Don't send an empty GetDetails to PackageKit

It's inefficient, and also makes PackageKit hang.
Merge branch 'b2.5'

Conflicts:
	ocaml/zeroinstall/downloader.ml