Fix buffer overflow in ByteParameter and protocol error with signed/unsigned types

[jrmelsha]

Identical behavior / style is now maintained between other integer types. Fixes the buffer overflow due to a misplaced sign/shift operation in the hex conversion code. Using hex also created issues with signed/unsigned compatibility and the server was rejecting inserts due to incorrectly thinking they were out of range.

[lawrinn]

Thanks for your PR!
Would it be possible to add a testcase for the problem you ares solving? That would make everybody's life easier, and also would help to avoid regressions. Since we are talking about the bug here, maybe the better idea is to open a ticket in jira.mariadb.org

But even before that, in order to accept the PR, we need you write in the comment, that you are contributing your new code of the whole pull request, including one or several files that are either new files or modified ones, under the BSD-new license.

[lawrinn]

I could not accept your contribution for licensing issues, but I've merged the testcase for your problem created by other contributor. I've opened the ticket for the problem https://jira.mariadb.org/browse/CONCPP-116 and fixed it my way. But thank you for the PR anyway - it helped to identify the problem.