tar: quote 'like this', not `like this'

This fixes some test failures recently introduced by gnulib updates
prompted by recent changes to the GNU coding standards,
which now advise to use quotes 'like this' or "like this"
rather than `like this'.
* NEWS: Document this.
* README, README-hacking, doc/Makefile.am, scripts/backup.in:
* scripts/backup.sh.in, scripts/dump-remind.in:
* src/buffer.c, src/checkpoint.c, src/create.c, src/incremen.c:
* src/misc.c, src/names.c, src/sparse.c, src/transform.c:
* tests/incr02.at, tests/incremental.at, tests/multiv08.at:
* tests/sparse04.at, tests/star/README, tests/update01.at:
Quote 'like this' in comments.
* src/tar.h:
Quote "like this" in comments, when quoting English phrases rather
than code.
* configure.ac:
* scripts/xsparse.c (get_var, read_xheader, main):
* src/compare.c (diff_archive):
* src/extract.c (prepare_to_extract):
* src/tar.c (request_stdin, tar_set_quoting_style, doc, options)
(set_subcommand_option, report_textual_dates, parse_opt)
(decode_options, main):
* src/xheader.c (decx):
Quote 'like this' in diagnostics.
* doc/tar.texi (list, warnings, override)
(Selecting Archive Members, quoting styles, after, hard links)
(Sparse Recovery, Multi-Volume Archives, label):
Adjust documentation to match new output.
* tests/backup01.at, tests/incr01.at, tests/incr04.at:
* tests/label04.at, tests/label05.at, tests/link03.at:
* tests/listed02.at, tests/multiv03.at, tests/multiv05.at:
* tests/rename01.at, tests/rename02.at, tests/rename03.at:
* tests/volume.at:
Adjust tests to match new quoting behavior.

scripts/backup.in

@@ -149,7 +149,7 @@ message 20 "BACKUP_DIRS=$BACKUP_DIRS"
 message 20 "BACKUP_FILES=$BACKUP_FILES"
 
 # The buch of commands below is run in a subshell for which all output is
-# piped through `tee' to the logfile.  Doing this, instead of having
+# piped through 'tee' to the logfile.  Doing this, instead of having
 # multiple pipelines all over the place, is cleaner and allows access to
 # the exit value from various commands more easily.
 (
@@ -187,7 +187,7 @@ message 20 "BACKUP_FILES=$BACKUP_FILES"
                 "--label='`print_level` backup of ${fs} on ${remotehost} at ${NOW}'" \
 		-C ${fs} .
 
-     # `rsh' doesn't exit with the exit status of the remote command.  What
+     # 'rsh' doesn't exit with the exit status of the remote command.  What
      # stupid lossage.  TODO: think of a reliable workaround.
      if [ $? -ne 0 ] ; then
 	 echo "Backup of ${1} failed." 1>&2