vma-iter: Add support for HP-UX. * modules/vma-iter (configure.ac): Check for 'pstat_getprocvm'. * lib/vma-iter.c (vma_iterate): On HP-UX, use pstat_getprocvm(). * lib/vma-iter.h (VMA_ITERATE_SUPPORTED): Define also on HP-UX. * lib/get-rusage-as.c: Update comment about HP-UX. * lib/get-rusage-data.c: Likewise. (get_rusage_data): Use get_rusage_data_via_setrlimit.