Add more xz compression support.

Add more xz compression support.

* doc/man/etags.1: xz compression is now supported.
* doc/misc/woman.texi (Interface Options): xz compression is now supported.

* lib-src/etags.c (compressors, print_language_names): Support xz compression.

* lisp/eshell/em-ls.el (eshell-ls-archive-regexp):
* lisp/eshell/esh-util.el (eshell-tar-regexp):
* lisp/ibuffer.el (ibuffer-compressed-file-name-regexp):
* lisp/info.el (Info-suffix-list):
* lisp/international/mule.el (auto-coding-alist):
* lisp/woman.el (woman-file-regexp, woman-file-compression-regexp):
* lisp/progmodes/etags.el (tags-compression-info-list):
Support xz compression.