This patch switches reg_file_entry structure with RegFileEntry
protobuf entry. Note that there a few nits remains

 - old fown_t structure doesn't scale well with FownEntry from
   RegFileEntry, so to not mess with rest of crtools code
   I've added a couple of opencoded copy operands, will clean
   this aspect up once rest of code is converted

 - the "show" procedure doesn't print fown for same reason

v2:
 - rename fown_t to fown_entry in .proto
v3:
 - don't print nil symbol on show
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>