genfstab: derive the real type of fuseblk filesystems
common: auto-register api_fs_umount EXIT trap

This corrects some weird/wrong EXIT trap decls in arch-chroot and
pacstrap that should have been touched as part of the cleanup in
517fcff074.
genfstab: prefer lsblk over blkid

lsblk has a far nicer interface and is capable of doing its work
without the need for extra privileges to read superblocks (assuming
udev is behaving properly).
genfstab: be more careful about assigning passno
Makefile: add check target for syntax check
prepare v11 release