HPCC-10921 Fix HASH/HASH64 on constant strings

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5505 from ghalliday/issue10921

HPCC-10921 Fix HASH/HASH64 on constant strings

Reviewed-By: Jamie Noss <james.noss@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>