Woodstox 5.1.0 released

[Tatu Saloranta]

Quick note: after couple of fixes, and addition of minimal Java 9 metadata, I decided to release 5.1.0. Release notes are as follows:

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5.1.0 (31-Mar-2018)

#23: Text content is not validated correctly when copying events to `XmlStreamWriter`

 (reported by hxc9@github)

#43: `CompactStartElement` appears to incorrectly classify attributes as default

 (reported by Jonathan T)

- Add `Automatic-Module-Name` indicator in jar metadata, for Java 9

- Upgrade `stax2-api` dependency to 4.1 (from 3.1)

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Baseline is still JDK 6, no major changes.

I will also release new minor version of Aalto XML processor soon.

Please let me know of new problems with this version, if any,

-+ Tatu +-