RHEL 5 complains on "warning: value computed is not used"
RHEL 5 does not have TAILQ_CONCAT

rdkafka.c includes rdkafka_int.h which uses TAILQ_CONCAT. Added rdsysqueue.h include to fix
RHEL 5 does not have htole16/le32toh

These are from RHEL 6 endian.h
Merge pull request #57 from stromnet/master

RHEL (CentOS) 5 compilation fixes