GH-18345: adding Locale::isRightToLeft.

Checks is the locale is written left to right.
It makes sure all the needed likely subtags are included (maximization)
then determines the direction by known matches.

Author: devnexen

ext/intl/locale/locale.stub.php

@@ -133,4 +133,9 @@ public static function canonicalize(string $locale): ?string {}
      * @alias locale_accept_from_http
      */
     public static function acceptFromHttp(string $header): string|false {}
+
+    /**
+     * @alias locale_is_right_to_left
+     */
+    public static function isRightToLeft(string $locale): bool {}
 }

ext/intl/locale/locale_arginfo.h

@@ -1619,3 +1619,19 @@ PHP_FUNCTION(locale_accept_from_http)
 	RETURN_STRINGL(resultLocale, len);
 }
 /* }}} */
+
+PHP_FUNCTION(locale_is_right_to_left)
+{
+	char *locale;
+	size_t locale_len;
+
+	ZEND_PARSE_PARAMETERS_START(1, 1)
+		Z_PARAM_STRING(locale, locale_len)
+	ZEND_PARSE_PARAMETERS_END();
+
+	if (!locale_len) {
+		locale = (char *)intl_locale_get_default();
+	}
+
+	RETURN_BOOL(uloc_isRightToLeft((const char *)locale));
+}

ext/intl/locale/locale_methods.c

@@ -0,0 +1,16 @@
+--TEST--
+locale_is_right_to_left
+--EXTENSIONS--
+intl
+--FILE--
+<?php
+var_dump(Locale::isRightToLeft("en-US"));
+var_dump(Locale::isRightToLeft("\INVALID\\"));
+var_dump(Locale::isRightToLeft(""));
+var_dump(Locale::isRightToLeft("ar"));
+?>
+--EXPECT--
+bool(false)
+bool(false)
+bool(false)
+bool(true)