* Makefile.util.def (libgrubmods.a): Add minilzo.c and add required flags
to cflags in cppflags.
* Makefile.core.def (btrfs): Likewise.
* grub-core/fs/btrfs.c: Include minilzo.h.
(grub_btrfs_superblock): Add sectorsize, nodesize, leafsize, stripsize and
dummy5 field.
(GRUB_BTRFS_COMPRESSION_LZO): New define.
(grub_btrfs_extent_read): Add support for LZO compression type.