* configure.ac: Remove checks for getfsstat() and getmntany().
Add checks for `<sys/param.h>' and `<sys/mount.h>'.
* kern/emu/misc.c [HAVE_GETMNTANY]: Remove `<sys/mnttab.h>'.
[HAVE_SYS_PARAM_H]: Include `<sys/param.h>'.
[HAVE_SYS_MOUNT_H]: Include `<sys/mount.h>'.
[HAVE_LIBZFS && HAVE_LIBNVPAIR] (find_mount_point_from_dir): Remove
function.
(grub_find_zpool_from_dir): Use statfs() instead of indirect matching
via find_mount_point_from_dir() and getfsstat() / getmntany().