Update THANKS.
liblzma: Fix lzma_mt.preset in lzma_stream_encoder_mt_memusage().

It read the filter chain from a wrong variable. This is a similar
bug that was fixed in 9494fb6d0ff41c585326f00aa8f7fe58f8106a5e.
xzdiff: Create a temporary directory to hold a temporary file.

This avoids the possibility of "File name too long" when
creating a temp file when the input file name is very long.

This also means that other users on the system can no longer
see the input file names in /tmp (or whatever $TMPDIR is)
since the temporary directory will have a generic name. This
usually doesn't matter since on many systems one can see
the arguments given to all processes anyway.

The number X chars to mktemp where increased from 6 to 10.

Note that with some shells temp files or dirs won't be used at all.
xzdiff: Use mkdir if mktemp isn't available.