Changes for compatibility with Slackware installation scripts.

* src/buffer.c (short_read): the "Record size" message
is controlled by the WARN_RECORD_SIZE warning_option bit.
* src/common.h (keep_directory_symlink_option): New global.
(WARN_RECORD_SIZE): New constant.
(WARN_VERBOSE_WARNINGS): Add WARN_RECORD_SIZE.
* src/extract.c (extract_dir): If keep_directory_symlink_option is
set, follow symlinks to directories.
* src/suffix.c (compression_suffixes): Add support for txz
suffix.
* src/tar.c (KEEP_DIRECTORY_SYMLINK_OPTION): New constant.
(options): New option --keep-directory-symlink.
(parse_opt): Handle this option.
* src/warning.c: Implement "record-size" warning control.

* NEWS: Update.
* doc/tar.texi: Document new features.