Merge branch 'update_xz' into 'master'

Remove customization of and update xz.

See merge request !246

recipes/xz/recipe.toml

 [source]
-tar = "https://codeload.github.com/xz-mirror/xz/tar.gz/v5.2.3"
-patches = [
-    "01-no-poll.patch",
-    "02-o_noctty.patch",
-    "03-no-signals.patch"
-]
-script = """
-./autogen.sh
-chmod +w build-aux/config.sub
-wget -O build-aux/config.sub http://git.savannah.gnu.org/cgit/config.git/plain/config.sub
-"""
+tar = "https://codeload.github.com/xz-mirror/xz/tar.gz/v5.2.5"
 
 [build]
 template = "custom"