Print ssl library version only on Qt >=5.0.0.
Propagator: Compare the actual file size with the request content length

The values must match. Otherwise the request did succeed, but the file
was not downloaded completely.

This fixes https://github.com/owncloud/mirall/issues/2528
FolderWatcherTest: Use Utility::usleep.
[tx-robot] updated from transifex
Propagator: only check the content-lenght if it is there

If content-lenght is 0, don't chack it is the size we recieved.
It can be zero when using HTTP chunk encoding.

Also do not remove the temporary file so it can be re-used on the next sync
and ask for a new sync immediatly to re-do the sync.

Fixup the fix to task #2528
Merge branch '1.7'