Canonicalize error

[microshine]

I have a simple progrem on C#.NET, it allows to get C14N and EXC-C14N results from XML

https://github.com/yaronn/xml-crypto/blob/master/test/canonicalization-unit-tests.js#L83-L89

I checked result for example from link. It has difference. Seems that the namespace processing is different

XML-CRYPTO result:

<p:child xmlns:inclusive="ns2" xmlns:p="ns"><inclusive:inner>123</inclusive:inner></p:child>

.NET EXC-C14N:

<p:child xmlns:p="ns"><inclusive:inner xmlns:inclusive="ns2">123</inclusive:inner></p:child>

.NET C14N:

<p:child xmlns:inclusive="ns2" xmlns:p="ns"><inclusive:inner>123</inclusive:inner></p:child>

[cjbarth]

@microshine , we'd be more than happy to see a PR with a test suite to address this concern.