Add SCRAM support

Hi list!

Hopefully this is good news, I have submitted a PR adding SCRAM
support to the driver:

https://github.com/pgjdbc/pgjdbc/pull/842

PR is very simple on itself, since most of the work has been done
on this external SCRAM library:

https://github.com/ongres/scram

This library was purpose-written for pgjdbc, but with the idea that
it could be easily re-used by third parties.

TODOs:

- pgjdbc:
* Patch is not integrated with current pgjdbc test system.
Contributions are welcome, I will focus my efforts on improving now the
library!
* I guess patch needs the "magic macros" that prevent the code from
being included in Java < 8 versions

- library:
* Current version is 1.0.0-beta2. I will bump the version to 1.0.0
once StringPrep support is added and any bugs are ironed out, such that
pgjdbc release will depend on 1.0.0.
* Library is currently decently tested (>70 unit tests) but more
work will be done here

Testing, contributions and ideas are welcome.

Thanks!

Álvaro

--

Álvaro Hernández Tortosa

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