Fixing undefined variable usage

Squash of pull request #872

lib/Cake/Cache/Engine/WincacheEngine.php

@@ -183,6 +183,7 @@ class WincacheEngine extends CacheEngine {
  * @return boolean success
  **/
 	public function clearGroup($group) {
+		$success = null;
 		wincache_ucache_inc($this->settings['prefix'] . $group, 1, $success);
 		return $success;
 	}

lib/Cake/Console/ShellDispatcher.php

@@ -215,7 +215,8 @@ class ShellDispatcher {
 				return $Shell->main();
 			}
 		}
-		throw new MissingShellMethodException(array('shell' => $shell, 'method' => $arg));
+		
+		throw new MissingShellMethodException(array('shell' => $shell, 'method' => $command));
 	}
 
 /**

lib/Cake/Model/Model.php

@@ -3250,7 +3250,7 @@ class Model extends Object implements CakeEventListener {
 			return array($with, array_unique(array_merge($assoc[$with], $keys)));
 		}
 		trigger_error(
-			__d('cake_dev', 'Invalid join model settings in %s', $model->alias),
+			__d('cake_dev', 'Invalid join model settings in %s. The association parameter has the wrong type, expecting a string or array, but was passed type: %s', $this->alias, gettype($assoc)),
 			E_USER_WARNING
 		);
 	}