[xmlsec] signing failure with 0.0.13 that work with 0.0.10

[Aleksey Sanin]

Oh, now I remember! Well, the main reason for this is that I would 
prefer to have
the same semantics for the Encryption and Signature. In encryption case, 
you can use
"--node-xpath" to specify the "start" node you want to encrypt. It seems 
logical to me,
that you can use the same option to specify the "start" node you want to 
sign, verify or
decrypt. However, I don't have any strong feeling about that so I can 
make it work
the way you need.

Aleksey