vm_map_find(9) on FreeBSD

The text 3eaab06a10f2, as FreeBSD 7.0-RELEASE, FreeBSD 6.3-RELEASE, FreeBSD 6.2-RELEASE, FreeBSD 6.1-RELEASE, FreeBSD 6.0-RELEASE shipped it.

find a free region within a map, and optionally map a vm_object