Optimize helper event listeners.

Most of the core helpers don't use event listeners. Stubbing out the
methods saves 6 calls to method_exists() per helper.

src/View/Helper/FormHelper.php

@@ -2171,4 +2171,13 @@ public function widget($name, array $data = []) {
 		return $this->_registry->get($name)->render($data);
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }

src/View/Helper/HtmlHelper.php

@@ -1237,4 +1237,13 @@ public function loadConfig($configFile, $path = null) {
 		return $configs;
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }

src/View/Helper/NumberHelper.php

@@ -218,4 +218,13 @@ public function defaultCurrency($currency) {
 		return $this->_engine->defaultCurrency($currency);
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }

src/View/Helper/PaginatorHelper.php

@@ -808,4 +808,13 @@ public function last($last = 'last >>', $options = array()) {
 		return $out;
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return ['View.beforeRender' => 'beforeRender'];
+	}
+
 }

src/View/Helper/RssHelper.php

@@ -351,4 +351,13 @@ public function elem($name, $attrib = array(), $content = null, $endTag = true)
 		return $xml;
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }

src/View/Helper/SessionHelper.php

@@ -158,4 +158,13 @@ public function valid() {
 		return Session::valid();
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }

src/View/Helper/TextHelper.php

@@ -325,4 +325,13 @@ public function toList($list, $and = 'and', $separator = ', ') {
 		return $this->_engine->toList($list, $and, $separator);
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }

src/View/Helper/TimeHelper.php

@@ -446,4 +446,13 @@ public function i18nFormat($date, $format = null, $invalid = false, $timezone =
 		return $this->_engine->i18nFormat($date, $format, $invalid, $timezone);
 	}
 
+/**
+ * Event listeners.
+ *
+ * @return array
+ */
+	public function implementedEvents() {
+		return [];
+	}
+
 }