[#2248] Make paver.sh correctly identify arch on Solaris.

Problem?
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`paver.sh` fails to identify 64-bit Solaris properly.

Solution?
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Cross-pollinate the recent Solaris-related improvements from `python-package`:

 * use a more portable `tr` invocation
 * use `isainfo` instead of `uname` in Solaris
 * use `x64` for `amd64` and `sparc64` for `sparcv9`.

How to test?
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Please review changes.
Issue `paver test_remote group-all`.

reviewer @adiroiban