Add test for iconv_mime_encode() for input-charset and output-charset

Closes GH-8766.

Author: jcm

ext/iconv/tests/iconv_mime_encode_001.phpt

@@ -0,0 +1,33 @@
+--TEST--
+iconv_mime_encode(): Encoding parameter exceeds the maximum allowed for preference "input-charset" and "output-charset"
+--EXTENSIONS--
+iconv
+--INI--
+iconv.internal_charset=iso-8859-1
+--FILE--
+<?php
+$extra = str_repeat("x", 256);
+
+$preferences = [
+    "input-charset" => "ISO-8859-1".$extra,
+    "output-charset" => "UTF-8",
+    "line-length" => 76,
+    "line-break-chars" => "\n",
+    "scheme" => "B"
+];
+
+$result = iconv_mime_encode("Subject", "Prüfung", $preferences);
+var_dump($result);
+
+$preferences["input-charset"] = "ISO-8859-1";
+$preferences["output-charset"] = "UTF-8".$extra;
+
+$result = iconv_mime_encode("Subject", "Prüfung", $preferences);
+var_dump($result);
+?>
+--EXPECTF--
+Warning: iconv_mime_encode(): Encoding parameter exceeds the maximum allowed length of %d characters in %s on line %d
+bool(false)
+
+Warning: iconv_mime_encode(): Encoding parameter exceeds the maximum allowed length of %d characters in %s on line %d
+bool(false)