Replace existing autoloader with Composer-supplied

- Move Friendica namespace to `src`
- Move required `ezyang/htmlpurifier` to vendor
- Remove existing static autoloader
- Change boot.php reference to the autoloader

vendor/ezyang/htmlpurifier/library/HTMLPurifier/AttrDef/CSS/Number.php

@@ -0,0 +1,84 @@
+<?php
+
+/**
+ * Validates a number as defined by the CSS spec.
+ */
+class HTMLPurifier_AttrDef_CSS_Number extends HTMLPurifier_AttrDef
+{
+
+    /**
+     * Indicates whether or not only positive values are allowed.
+     * @type bool
+     */
+    protected $non_negative = false;
+
+    /**
+     * @param bool $non_negative indicates whether negatives are forbidden
+     */
+    public function __construct($non_negative = false)
+    {
+        $this->non_negative = $non_negative;
+    }
+
+    /**
+     * @param string $number
+     * @param HTMLPurifier_Config $config
+     * @param HTMLPurifier_Context $context
+     * @return string|bool
+     * @warning Some contexts do not pass $config, $context. These
+     *          variables should not be used without checking HTMLPurifier_Length
+     */
+    public function validate($number, $config, $context)
+    {
+        $number = $this->parseCDATA($number);
+
+        if ($number === '') {
+            return false;
+        }
+        if ($number === '0') {
+            return '0';
+        }
+
+        $sign = '';
+        switch ($number[0]) {
+            case '-':
+                if ($this->non_negative) {
+                    return false;
+                }
+                $sign = '-';
+            case '+':
+                $number = substr($number, 1);
+        }
+
+        if (ctype_digit($number)) {
+            $number = ltrim($number, '0');
+            return $number ? $sign . $number : '0';
+        }
+
+        // Period is the only non-numeric character allowed
+        if (strpos($number, '.') === false) {
+            return false;
+        }
+
+        list($left, $right) = explode('.', $number, 2);
+
+        if ($left === '' && $right === '') {
+            return false;
+        }
+        if ($left !== '' && !ctype_digit($left)) {
+            return false;
+        }
+
+        $left = ltrim($left, '0');
+        $right = rtrim($right, '0');
+
+        if ($right === '') {
+            return $left ? $sign . $left : '0';
+        } elseif (!ctype_digit($right)) {
+            return false;
+        }
+        return $sign . $left . '.' . $right;
+    }
+}
+
+// vim: et sw=4 sts=4