HPCC-9999 Correctly export functions so hql.dll links on windows

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4815 from ghalliday/issue9999

HPCC-9999 Correctly export functions so hql.dll links on windows

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>