[xmlsec] namespace prefixes on Signature

[Aleksey Sanin]

> I'm not sure one *can* insert the namespace without this function.  I've 
> not found anything in libxml2 that allows for manipulation of namespace 
> after definition.
> 
> My read is that both the new function and search change are required to 
> get prefixes attach to all the dsig elements.  Would it be 
> over-engineering to create a new xmlSecAddChild() function to allow for 
> the different search approach?

You don't need this! After xmlSearchNs() => xmlSearchNsByHref() change
you would simply need to insert xmldsig namespace with any desired
prefix anywhere in the DOM tree above the Signature node (e.g. in the
root node) and then xmlSecTmplSignatureCreate() and all other xmlsec
template functions will simply use :)

Aleksey