Add test to exercise _php_mb_encoding_handler_ex with multiple possible input encodings

Thanks to Kamil Tekiela for pointing out that there was no test
case for this.

Author: alexdowad

ext/mbstring/tests/mb_parse_str_multi.phpt

@@ -0,0 +1,38 @@
+--TEST--
+mb_parse_str() with multiple candidate encodings
+--EXTENSIONS--
+mbstring
+--INI--
+mbstring.http_input=UTF-8,SJIS,EUC-JP
+--FILE--
+<?php
+// The encoding of the input strings will be guessed, from the list specified
+// via mbstring.http_input
+// All of them will be converted to UTF-8
+mb_internal_encoding('UTF-8');
+
+$queries = array(
+  // UTF-8
+  "テスト=abc",
+  // SJIS
+  "\x82\xA0\x82\xA2\x82\xA4=\x93V"
+);
+
+foreach ($queries as $query) {
+  echo "Query: " . bin2hex($query) . "\n";
+
+  $array = [];
+  mb_parse_str($query, $array);
+
+  foreach ($array as $key => $value) {
+    echo bin2hex($key) . "=>" . bin2hex($value) . "\n";
+  }
+}
+
+?>
+--EXPECTF--
+Deprecated: PHP Startup: Use of mbstring.http_input is deprecated in %s on line %d
+Query: e38386e382b9e383883d616263
+e38386e382b9e38388=>616263
+Query: 82a082a282a43d9356
+e38182e38184e38186=>e5a4a9