sysutils/fusefs-lkl: Add lklfuse, a Linux implementation for FUSE

liblkl.a provides the Linux kernel (in nommu mode) as a library. The lklfuse
binary can be used to mount filesystems that Linux supports (btrfs, ext4 and
earlier, and xfs) read/write under FUSE.

Reviewed by: bdrewery
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D4199