MFC r322665Add caveat to kinfo_getvmmap(3) explaining high CPU utilisation.Based on kib's reply on https://lists.freebsd.org/pipermail/freebsd-hackers/2016-July/049710.html
MFC 283622:Add <sys/user.h> to the SYNOPSIS of the kinfo_get*() functions since thesefunctions all return types that are defined in that header.