HPCC-9553 Support typedefs as the base type for ENUM definitions

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4799 from ghalliday/issue9553

HPCC-9553 Support typedefs as the base type for ENUM definitions

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>