Testcase:
21 01 01 00 00 00 00 00 e7 01 01 01 ef 00 df b6
00 17 02 10 11 0f ff 00 16 00 00
Unfortunately, the bug is not reliably causing a segfault,
the behavior depends on what's in memory before the buffer.
function old new delta
unpack_lzma_stream 2762 2768 +6
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>