Undo previous mbstring function replacements

This reverts commits:

 - 6b28381
 - c7331db
 - 82421eb

composer.json

@@ -17,10 +17,8 @@
         "colinodell/commonmark-php": "*"
     },
     "require": {
-        "php": ">=5.3.3"
-    },
-    "suggest": {
-        "ext-mbstring": "Enables faster performance when normalizing link references"
+        "php": ">=5.3.3",
+        "ext-mbstring": "*"
     },
     "require-dev": {
         "erusev/parsedown": "~1.0",

src/Reference/Reference.php

@@ -14,8 +14,6 @@
 
 namespace League\CommonMark\Reference;
 
-use League\CommonMark\Util\UnicodeCaseFolder;
-
 /**
  * Link reference
  */
@@ -89,12 +87,6 @@ public static function normalizeReference($string)
         // leading/trailing whitespace
         $string = preg_replace('/\s+/', '', trim($string));
 
-        // Convert to upper-case using Unicode case folding
-        // Use an alternate method if mb_strtoupper isn't available
-        if (!function_exists('mb_strtoupper')) {
-            return UnicodeCaseFolder::toUpperCase($string);
-        }
-
         return mb_strtoupper($string, 'UTF-8');
     }
 }

src/Util/Html5Entities.php

@@ -2283,7 +2283,7 @@ public static function fromDecimal($number)
 
         $entity = '&#' . $number . ';';
 
-        $converted = html_entity_decode($entity, ENT_COMPAT, 'UTF-8');
+        $converted = mb_decode_numericentity($entity, array(0x0, 0x2FFFF, 0, 0xFFFF), 'UTF-8');
 
         if ($converted === $entity) {
             return self::fromHex('fffd');

src/Util/TextHelper.php

@@ -36,8 +36,7 @@ public static function detabLine($string)
 
         foreach ($parts as $part) {
             // Calculate number of spaces; insert them followed by the non-tab contents
-            $lineLength = strlen(utf8_decode($line));
-            $amount = 4 - $lineLength % 4;
+            $amount = 4 - mb_strlen($line, 'UTF-8') % 4;
             $line .= str_repeat(' ', $amount) . $part;
         }