Upgrade to XZ 1.7

1.8 (2018-01-04)

    * Fix a binary compatibility regression: XZ for Java 1.7 binaries
      in the Maven Central require Java 9 which is too new. XZ for
      Java 1.8 binaries require Java 5. (XZ for Java 1.6 and older
      binaries require Java 1.4.)

      If you are using OpenJDK 9 or later, you will need to edit the
      "sourcever = 1.5" line in the file "build.properties" before
      running "ant". Set it to 1.6 or higher. The default value 1.5
      isn't supported by OpenJDK 9 or later.

    * Add "Automatic-Module-Name" = "org.tukaani.xz".

1.7 (2017-12-29)

    * Fix LZMA2InputStream.available() which could return a too high
      value in case of uncompressed LZMA2 chunks. This incorrect
      value was visible via other available() methods too, for example,
      XZInputStream.available().

    * Add the ArrayCache API. It's a pool-like API to reuse large byte
      and int arrays between compressor and decompressor instances.
      If you are (de)compressing many tiny files in a row, taking
      advantage of this API can improve performance significantly.