ext/gettext/tests: fix libintl return values under musl

Musl has two quirks that are leading to failed internationalization
tests. First is that the return value of bindtextdomain(..., NULL)
will always be false, rather than an "implementation-defined default
directory," because musl does not have an implementation-defined
default directory. One test needs a special case for this.

Second is that the musl implementation of bind_textdomain_codeset()
always returns NULL. The POSIX-correctness of this is debatable, but
it is roughly equivalent to correct, because musl only support UTF-8,
so the NULL value indicating that the codeset is unchanged from the
locale's codeset (UTF-8) is accurate.

PHP's bind_textdomain_codeset() function however treats NULL as
failure, unconditionally:

  * php/doc-en#4311
  * php#17163

This unfortunately causes false to be returned consistently on musl --
even when nothing unexpected has happened -- and naturally this is
affecting several tests. For now we change two tests to accept "false"
in addition to "UTF-8" so that they may pass on musl. If PHP's
bind_textdomain_codeset() is updated to differentiate between NULL and
NULL-with-errno-set, these tests can also be updated once again to
reject the NULL-with-errno result.

This partially addresses GH php#13696

ext/gettext/tests/bug53251.phpt

@@ -8,18 +8,28 @@ if (getenv('SKIP_REPEAT')) die('skip gettext leaks global state across requests'
 ?>
 --FILE--
 <?php
-var_dump(is_string(bindtextdomain('foo', null)));
+$results[] = is_string(bindtextdomain('foo', null));
 $dir = bindtextdomain('foo', '.');
-var_dump(bindtextdomain('foo', null) === $dir);
+$results[] = bindtextdomain('foo', null) === $dir;
+$results[] = bind_textdomain_codeset('foo', null);
+$results[] = bind_textdomain_codeset('foo', 'UTF-8');
+$results[] = bind_textdomain_codeset('foo', null);
 
-var_dump(bind_textdomain_codeset('foo', null));
-var_dump(bind_textdomain_codeset('foo', 'UTF-8'));
-var_dump(bind_textdomain_codeset('foo', null));
+$expected = [true, true, false, "UTF-8", "UTF-8"];
 
+// musl's bindtextdomain() has no default directory to return when
+// "foo" is unbound, so in the first call, you will get false instead
+// of a string.
+//
+// bind_textdomain_codeset() always returns false on musl
+// because musl only supports UTF-8. For more information:
+//
+//   * https://github.com/php/doc-en/issues/4311,
+//   * https://github.com/php/php-src/issues/17163
+//
+$expected_musl = [false, true, false, false, false];
+
+var_dump($results === $expected or $results === $expected_musl);
 ?>
 --EXPECT--
 bool(true)
-bool(true)
-bool(false)
-string(5) "UTF-8"
-string(5) "UTF-8"

ext/gettext/tests/gettext_bind_textdomain_codeset-retval.phpt

@@ -15,14 +15,22 @@ gettext
     } catch (ValueError $e) {
 	    echo $e->getMessage() . PHP_EOL;
     }
-    var_dump(bind_textdomain_codeset('messages', "UTF-8"));
+
+    // bind_textdomain_codeset() always returns false on musl
+    // because musl only supports UTF-8. For more information:
+    //
+    //   * https://github.com/php/doc-en/issues/4311,
+    //   * https://github.com/php/php-src/issues/17163
+    //
+    $result = bind_textdomain_codeset('messages', "UTF-8");
+    var_dump($result === false or $result === "UTF-8");
 
     echo "Done\n";
 ?>
 --EXPECT--
 bind_textdomain_codeset(): Argument #1 ($domain) must not be empty
 bind_textdomain_codeset(): Argument #1 ($domain) must not be empty
-string(5) "UTF-8"
+bool(true)
 Done
 --CREDITS--
 Florian Holzhauer [email protected]