decompress_unxz: newer version, one which can unpack SHA-256 protected files

function                                             old     new   delta
check_sizes                                            -      16     +16
crc32_table                                            -       4      +4
index_update                                          47      40      -7
crc32_validate                                       110      93     -17
dec_vli                                              197     165     -32
unpack_xz_stream                                    4284    4014    -270
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/4 up/down: 20/-326)          Total: -306 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/archival/libunarchive/unxz/xz_config.h b/archival/libunarchive/unxz/xz_config.h
index 3259815..ff90eff 100644
--- a/archival/libunarchive/unxz/xz_config.h
+++ b/archival/libunarchive/unxz/xz_config.h
@@ -43,7 +43,7 @@
  * becomes slow.
  *
  * NOTE: System headers on GNU/Linux may #define this macro already,
- * so if you want to change it, it you need to #undef it first.
+ * so if you want to change it, you need to #undef it first.
  */
 #ifndef __always_inline
 #	ifdef __GNUC__
@@ -114,6 +114,8 @@
  * little endian systems, #define get_le32(ptr) (*(const uint32_t *)(ptr))
  * could save a few bytes in code size.
  */
-#define get_le32 get_unaligned_le32
+#ifndef get_le32
+#	define get_le32 get_unaligned_le32
+#endif
 
 #endif