*: teach tar et. al. to understand .xz by heart

function                                             old     new   delta
unpack_xz_stream                                       -    4126   +4126
setup_unzip_on_fd                                     80     150     +70
open_zipped                                          113     131     +18
unpack_unxz                                            5      12      +7
send_tree                                            360     353      -7
unpack_xz_stream_stdin                              3953       -   -3953
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 3/1 up/down: 4221/-3960)        Total: 261 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/unarchive.h b/include/unarchive.h
index 14cd98e..783a943 100644
--- a/include/unarchive.h
+++ b/include/unarchive.h
@@ -143,14 +143,15 @@
 } inflate_unzip_result;
 
 IF_DESKTOP(long long) int inflate_unzip(inflate_unzip_result *res, off_t compr_size, int src_fd, int dst_fd) FAST_FUNC;
-IF_DESKTOP(long long) int unpack_xz_stream_stdin(void) FAST_FUNC;
+/* xz unpacker takes .xz stream from offset 0 */
+IF_DESKTOP(long long) int unpack_xz_stream(int src_fd, int dst_fd) FAST_FUNC;
 /* lzma unpacker takes .lzma stream from offset 0 */
 IF_DESKTOP(long long) int unpack_lzma_stream(int src_fd, int dst_fd) FAST_FUNC;
 /* the rest wants 2 first bytes already skipped by the caller */
 IF_DESKTOP(long long) int unpack_bz2_stream(int src_fd, int dst_fd) FAST_FUNC;
 IF_DESKTOP(long long) int unpack_gz_stream(int src_fd, int dst_fd) FAST_FUNC;
 IF_DESKTOP(long long) int unpack_gz_stream_with_info(int src_fd, int dst_fd, unpack_info_t *info) FAST_FUNC;
-IF_DESKTOP(long long) int unpack_Z_stream(int fd_in, int fd_out) FAST_FUNC;
+IF_DESKTOP(long long) int unpack_Z_stream(int src_fd, int dst_fd) FAST_FUNC;
 /* wrapper which checks first two bytes to be "BZ" */
 IF_DESKTOP(long long) int unpack_bz2_stream_prime(int src_fd, int dst_fd) FAST_FUNC;