This brings support for multi-threaded compression. This brings close
N times faster compression where N is the number of CPU cores.
Because of this, liblzma now depends on libthr.
Soon libarchive will be modified to use the new lzma API.
Thanks to antoine@ for the exp-run.
Differential Revision: https://reviews.freebsd.org/D1786
Reviewed by: bapt
emulation of misaligned memory accesses). We cannot map the unaligned
memory access functions to the ones used for aligned accesses, so do
not define TUKLIB_FAST_UNALIGNED_ACCESS.