Instead of returning lowercase characters with BASIC's HEX command, uppercase characters are now returned. Digits from 0-9 are not affected. This change utilizes on OUString's toAsciiUpperCase() method.

Change-Id: Id6ea93a7635c1913c8592bf5519bdd7391f4e3bc
Reviewed-on: https://gerrit.libreoffice.org/1428Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>