Record the file size as Metadata.size when possible.
Record the file size as Metadata.size when possible.

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>
Reviewed-by: Zoran Zaric <d7dacae2c968388960bf8970080a980ed5c5dcb7@zoranzaric.de>

jbaber/bup,ToxicFrog/bup,pombredanne/bup,mhoeher/bup,apenwarr/bup,pombredanne/bup,mhoeher/bup,jbaber/bup,ToxicFrog/bup,tjanez/bup,apenwarr/bup,jbaber/bup,jbaber/bup,gevaerts/bup,tjanez/bup,apenwarr/bup,pombredanne/bup,mhoeher/bup,pombredanne/bup,pombredanne/bup,tjanez/bup,pombredanne/bup,tjanez/bup,jbaber/bup,tjanez/bup,gevaerts/bup,gevaerts/bup,tjanez/bup,jbaber/bup,ToxicFrog/bup,mhoeher/bup,mhoeher/bup,gevaerts/bup,ToxicFrog/bup,ToxicFrog/bup,gevaerts/bup,mhoeher/bup,apenwarr/bup