Drop ext-libxml requirement

Fixes #174

Author: alecpl

composer.json

@@ -22,7 +22,6 @@
     "require" : {
         "ext-ctype": "*",
         "ext-dom": "*",
-        "ext-libxml" : "*",
         "php" : ">=5.3.0"
     },
     "require-dev": {

src/HTML5/Parser/UTF8Utils.php

@@ -38,7 +38,7 @@ class UTF8Utils
 
     /**
      * Count the number of characters in a string.
-     * UTF-8 aware. This will try (in order) iconv, MB, libxml, and finally a custom counter.
+     * UTF-8 aware. This will try (in order) iconv, MB, and finally a custom counter.
      *
      * @param string $string
      *
@@ -55,12 +55,6 @@ public static function countChars($string)
             return iconv_strlen($string, 'utf-8');
         }
 
-        if (function_exists('utf8_decode')) {
-            // MPB: Will this work? Won't certain decodes lead to two chars
-            // extrapolated out of 2-byte chars?
-            return strlen(utf8_decode($string));
-        }
-
         $count = count_chars($string);
 
         // 0x80 = 0x7F - 0 + 1 (one added to get inclusive range)