Various squash4 fixes and LZO and XZ support.

	Various squash4 fixes and LZO and XZ support.

	* Makefile.util.def (libgrubmods.a): Add xzembed directory to cppflags.
	Add xzembed source files.
	* grub-core/Makefile.core.def (squash4): Add xzembed and minilzo flags.
	* grub-core/fs/squash4.c (grub_squash_super): New field compression.
	(grub_squash_inode): New subtype long_dir.
	(SQUASH_TYPE_LONG_DIR): New inode type.
	(COMPRESSION): New enum.
	(XZBUFSIZ): New const.
	(grub_squash_data): New fields blksz, decompress, xzdec, xzbuf.
	(read_chunk): Use data->decompress.
	(zlib_decompress): New function.
	(lzo_decompress): Likewise.
	(xz_decompress): Likewise.
	(squash_mount): Set new data fields.
	(grub_squash_iterate_dir): Handle long dir.
	(squash_unmount): Free xzdec and xzbuf.
	(grub_squash_open): Check ino type.
	(direct_read): Stylistic fixes. Use data->decompress.
	(grub_squash_read_data): Likewise.
	* grub-core/io/gzio.c (grub_gzio): Remove disk_input.
	(get_byte): Likewise.
	(grub_zlib_disk_read): Removed.
	* grub-core/lib/posix_wrap/sys/types.h (ssize_t): New type.
	(GRUB_POSIX_BOOL_DEFINED): New define.
	* grub-core/lib/posix_wrap/unistd.h: Include sys/types.h.
	* grub-core/lib/xzembed/xz.h: Addmissing includes.
	[!GRUB_POSIX_BOOL_DEFINED]: Define bool.
	* include/grub/deflate.h (grub_zlib_disk_read): Removed.