Exim 0.55 fails hpux9.05

gcc -c -g -O3 -I. deliver.c
deliver.c: In function `deliver_local':
deliver.c:573: `RLIMIT_CORE' undeclared (first use this function)
deliver.c:573: (Each undeclared identifier is reported only once
deliver.c:573: for each function it appears in.)