Added support for .tar.xz compression format for data downloader,
xz gives 30% better compression than plain zip, but you need to
create zip archive with no compression: zip -0 -r, then
compress it with xz: xz -8 < archive.zip > archive.zip.xz
Data downloader will try to use xz decompressor on
anything with extension .zip.xz
Removed links to old deprecated NDK versions
Updated OpenTTD