Concatenated .xz should decompress to one stream

[mycl]

If you concatenate two .xz files and decompress them they should come out as one stream.

For example:

m@air:~/tmp$ echo Hello | xz > hi.xz
m@air:~/tmp$ cat hi.xz hi.xz > hi2.xz
m@air:~/tmp$ xzcat hi2.xz
Hello
Hello

>>> import lzma
>>> print lzma.open('hi2.xz').read()
>>> print lzma.LZMAFile('hi2.xz').read()
Hello