Remove obsolete global database_ctype_is_c.

Now that tsearch uses the database default locale, there's no need to
track the database CTYPE separately.

Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/0151ad01239e2cc7b3139644358cf8f7b9622ff7.camel@j-davis.com

src/backend/utils/adt/pg_locale.c

@@ -100,9 +100,6 @@ char	   *localized_full_days[7 + 1];
 char	   *localized_abbrev_months[12 + 1];
 char	   *localized_full_months[12 + 1];
 
-/* is the databases's LC_CTYPE the C locale? */
-bool		database_ctype_is_c = false;
-
 static pg_locale_t default_locale = NULL;
 
 /* indicates whether locale information cache is valid */

src/backend/utils/init/postinit.c

@@ -430,10 +430,6 @@ CheckMyDatabase(const char *name, bool am_superuser, bool override_allow_connect
 						   " which is not recognized by setlocale().", ctype),
 				 errhint("Recreate the database with another locale or install the missing locale.")));
 
-	if (strcmp(ctype, "C") == 0 ||
-		strcmp(ctype, "POSIX") == 0)
-		database_ctype_is_c = true;
-
 	init_database_collation();
 
 	/*

src/include/utils/pg_locale.h

@@ -39,9 +39,6 @@ extern PGDLLIMPORT char *localized_full_days[];
 extern PGDLLIMPORT char *localized_abbrev_months[];
 extern PGDLLIMPORT char *localized_full_months[];
 
-/* is the databases's LC_CTYPE the C locale? */
-extern PGDLLIMPORT bool database_ctype_is_c;
-
 extern bool check_locale(int category, const char *locale, char **canonname);
 extern char *pg_perm_setlocale(int category, const char *locale);