Fix request #7273: Files with French characters in name do not open in SVN

Also includes:
* Fix for usage of extra svn command (like annotate) that were
not working properly with utf8 files.
* Fix for sending utf8 content, files were transfered without charset. Force it
to be utf8

Change-Id: I0db90d79315367821d9be6418e7ffa6a3502d341