Don't abuse "`" to mean open quote.

This was appropriate before Unicode, where "`" and "'" often balanced
in visual output, but that's been obsolete for a while.
Overall, single-quote 'like this' instead of `like this', and
double-quote "like this" or (in typeset output) “like this”
instead of ``like this''.  While we're at it, fix some glitches
with hyphens versus minus versus en dash versus em dash.
* Makefile ($(MANTXTS)): Use UTF-8 locale to produce *.txt output.
* checktab.awk, tzselect.ksh:
Quote 'like this' in diagnostics, instead of `like this'.
* date.1, newctime.3, newtzset.3, time2posix.3, zic.8 (q, lq, rq):
New macros.  Use them for better double-quoting in output.
* workman.sh: Tell Perl that its stdin and stdout are UTF-8.
* NEWS: Document this.

etcetera

@@ -14,7 +14,7 @@ Zone	Etc/UTC		0	-	UTC
 Zone	Etc/UCT		0	-	UCT
 
 # The following link uses older naming conventions,
-# but it belongs here, not in the file `backward',
+# but it belongs here, not in the file 'backward',
 # as functions like gmtime load the "GMT" file to handle leap seconds properly.
 # We want this to work even on installations that omit the other older names.
 Link	Etc/GMT				GMT