Use version for builtin collations.

Given that the version field already exists, there's little reason not
to use it. Suggestion from Peter Eisentraut.

Discussion: https://postgr.es/m/613c120a-5413-4fa7-a501-6590eae558f8@eisentraut.org
Reviewed-by: Peter Eisentraut

src/backend/utils/adt/pg_locale.c

@@ -1732,13 +1732,23 @@ get_collation_actual_version(char collprovider, const char *collcollate)
 
 	/*
 	 * The only two supported locales (C and C.UTF-8) are both based on memcmp
-	 * and are not expected to change.
+	 * and are not expected to change, but track the version anyway.
 	 *
 	 * Note that the character semantics may change for some locales, but the
 	 * collation version only tracks changes to sort order.
 	 */
 	if (collprovider == COLLPROVIDER_BUILTIN)
-		return NULL;
+	{
+		if (strcmp(collcollate, "C") == 0)
+			return "1";
+		else if (strcmp(collcollate, "C.UTF-8") == 0)
+			return "1";
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("invalid locale name \"%s\" for builtin provider",
+							collcollate)));
+	}
 
 #ifdef USE_ICU
 	if (collprovider == COLLPROVIDER_ICU)

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202403272
+#define CATALOG_VERSION_NO	202403291
 
 #endif

src/include/catalog/pg_collation.dat

@@ -25,13 +25,13 @@
   collcollate => 'POSIX', collctype => 'POSIX' },
 { oid => '962', descr => 'sorts by Unicode code point, C character semantics',
   collname => 'ucs_basic', collprovider => 'b', collencoding => '6',
-  colllocale => 'C' },
+  colllocale => 'C', collversion => '1' },
 { oid => '963',
   descr => 'sorts using the Unicode Collation Algorithm with default settings',
   collname => 'unicode', collprovider => 'i', collencoding => '-1',
   colllocale => 'und' },
 { oid => '811', descr => 'sorts by Unicode code point; Unicode and POSIX character semantics',
   collname => 'pg_c_utf8', collprovider => 'b', collencoding => '6',
-  colllocale => 'C.UTF-8' },
+  colllocale => 'C.UTF-8', collversion => '1' },
 
 ]