New Code!
Postoffice has been upgraded to version 1.1.10 1.1.11. This release is because of a recent(?) enhancement to NetBSD where they depreciated statfs() by the simple expedient of stripping out the definition of struct statfs while leaving the function call in libc (and leaving the manpage to say that the structure can be found in the traditional include files that had been swept free of the evil taint of backward compatability.) This makes my traditional approach of checking to see if the function exists, then assuming that the header files associated with the function will actually contain stuff having to do with the function a somewhat less than useful approach. So I've redone the configure scripts to check for both statfs() and struct statfs, and to have postoffice pay attention to all the appropriate definitions when building.
There is no guarantee that this new code will actually work on a system that only has statvfs, because all of my development machines are old enough so that they don't have the New Standard Function installed on them. But it does configure and build properly on FreeBSD 4.8 and Mastodon INSTsomethingrecent, so there's actually a fighting chance that it will just work™ on a new machine.
(h/t to Pierre-Philipp Braun for the bug report and for giving me an account on his system for debugging)