utf8_tohtml: add $all param to encode everything (default false)

This is useful when every character needs to be converted to HTML entities, e.g. (email) `obfuscate()`. Respective test has also been added.

_test/tests/inc/utf8_html.test.php

@@ -11,6 +11,12 @@ class utf8_html_test extends DokuWikiTest {
         $this->assertEquals(utf8_tohtml($in),$out);
     }
 
+    function test_from_1byte_all(){
+        $in  = 'a';
+        $out = 'a';
+        $this->assertEquals(utf8_tohtml($in, true),$out);
+    }
+
     function test_from_2byte(){
         $in  = "\xc3\xbc";
         $out = 'ü';

inc/utf8.php

@@ -569,12 +569,13 @@ if(!function_exists('utf8_tohtml')){
      * @link   http://php.net/manual/en/function.utf8-decode.php
      *
      * @param string $str
+     * @param bool $all Encode non-utf8 char to HTML as well
      * @return string
      */
-    function utf8_tohtml ($str) {
+    function utf8_tohtml($str, $all = false) {
         $ret = '';
         foreach (utf8_to_unicode($str) as $cp) {
-            if ($cp < 0x80)
+            if ($cp < 0x80 && !$all)
                 $ret .= chr($cp);
             elseif ($cp < 0x100)
                 $ret .= "&#$cp;";