setup: use a more strict way to test BSD or OSX's statfs We want to use the `f_fstypename` field to get the filesystem type. Test it directly. The new macro HAVE_BSD_STATFS implys the old HAVE_SYS_MOUNT_H and HAVE_SYS_PARAM_H. So the latter ones are removed.

debugfsinfo: use util.getfstype This changes the behavior slightly. It now always prints fstype, regardless of whether osutil.getfstype exists.