Restore initdb's old behavior of always setting the lc_xxx GUCs.

In commit 3e51b27 I (tgl) caused initdb to leave lc_messages and
other lc_xxx GUCs commented-out in the installed postgresql.conf file
if they were going to be set to 'C'.  This was a hack for cosmetic
purposes, and it was buggy because lc_messages' wired-in default is
not 'C' but '' (empty string).  That led to --no-locale not having
the expected effect, since the postmaster would then obtain
lc_messages from its startup environment.

Let's just revert to the prior behavior of always de-commenting the
lc_xxx entries; the argument for changing that longstanding behavior
was weak in the first place.

Also, fix postgresql.conf.sample's erroneous claim that the default
value of lc_messages is 'C'.  I suspect that was what misled me into
making this mistake in the first place.

Report and patch by Kyotaro Horiguchi.  Back-patch to v16 where
the problem was introduced.

Discussion: https://postgr.es/m/20231122.162700.1995154567625541112.horikyota.ntt@gmail.com

Author: tglsfdc

src/backend/utils/misc/postgresql.conf.sample

@@ -734,7 +734,7 @@
 					# encoding
 
 # These settings are initialized by initdb, but they can be changed.
-#lc_messages = 'C'			# locale for system error message
+#lc_messages = ''			# locale for system error message
 					# strings
 #lc_monetary = 'C'			# locale for monetary formatting
 #lc_numeric = 'C'			# locale for number formatting

src/bin/initdb/initdb.c

@@ -1227,25 +1227,17 @@ setup_config(void)
 	conflines = replace_guc_value(conflines, "shared_buffers",
 								  repltok, false);
 
-	/*
-	 * Hack: don't replace the LC_XXX GUCs when their value is 'C', because
-	 * replace_guc_value will decide not to quote that, which looks strange.
-	 */
-	if (strcmp(lc_messages, "C") != 0)
-		conflines = replace_guc_value(conflines, "lc_messages",
-									  lc_messages, false);
+	conflines = replace_guc_value(conflines, "lc_messages",
+								  lc_messages, false);
 
-	if (strcmp(lc_monetary, "C") != 0)
-		conflines = replace_guc_value(conflines, "lc_monetary",
-									  lc_monetary, false);
+	conflines = replace_guc_value(conflines, "lc_monetary",
+								  lc_monetary, false);
 
-	if (strcmp(lc_numeric, "C") != 0)
-		conflines = replace_guc_value(conflines, "lc_numeric",
-									  lc_numeric, false);
+	conflines = replace_guc_value(conflines, "lc_numeric",
+								  lc_numeric, false);
 
-	if (strcmp(lc_time, "C") != 0)
-		conflines = replace_guc_value(conflines, "lc_time",
-									  lc_time, false);
+	conflines = replace_guc_value(conflines, "lc_time",
+								  lc_time, false);
 
 	switch (locale_date_order(lc_time))
 	{