Allow unrecognized encoding names in locales, as long as they're the same.

The buildfarm says commit 58274728 doesn't
work so well on Windows.  This is because the encoding part of Windows
locale names can be just a code page number, eg "1252", which we don't
consider to be a valid encoding name.  Add a check to accept encoding
parts that are case-insensitively string equal; this at least ensures
that the new code doesn't reject any cases that the old code allowed.

contrib/pg_upgrade/check.c

@@ -437,8 +437,14 @@ equivalent_locale(const char *loca, const char *locb)
 	if (!chara || !charb)
 		return (pg_strcasecmp(loca, locb) == 0);
 
-	/* Compare the encoding parts. */
-	if (!equivalent_encoding(chara + 1, charb + 1))
+	/*
+	 * Compare the encoding parts.	Windows tends to use code page numbers for
+	 * the encoding part, which equivalent_encoding() won't like, so accept if
+	 * the strings are case-insensitive equal; otherwise use
+	 * equivalent_encoding() to compare.
+	 */
+	if (pg_strcasecmp(chara + 1, charb + 1) != 0 &&
+		!equivalent_encoding(chara + 1, charb + 1))
 		return false;
 
 	/*