FEATURE: Make sure namespaces are only applied for Tx_ class definitions

* E.g. prevent migration for ux_ classes which do not follow the
  convention.
* Add test to make sure it works as expected.

src/Standards/Typo3Update/Sniffs/LegacyClassname/MissingNamespaceSniff.php

@@ -67,6 +67,9 @@ class Typo3Update_Sniffs_LegacyClassname_MissingNamespaceSniff implements PhpCsS
         }
 
         $classname = $tokens[$classnamePosition]['content'];
+        if (substr($classname, 0, 3) !== 'Tx_') {
+            return;
+        }
 
         LegacyClassnameMapping::getInstance()->addLegacyClassname(
             $classname,

tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassname/MissingNamespaceSniff/alreadyMigrated/Expected.json

@@ -0,0 +1,14 @@
+{
+    "files": {
+        "InputFileForIssues.php": {
+            "errors": 0,
+            "messages": [],
+            "warnings": 0
+        }
+    },
+    "totals": {
+        "errors": 0,
+        "fixable": 0,
+        "warnings": 0
+    }
+}

tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassname/MissingNamespaceSniff/alreadyMigrated/InputFileForIssues.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Vendor\ExtName\Controller;
+
+/*
+ * Copyright (C) 2017  Daniel Siepmann <coding@daniel-siepmann.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+use Tx_Extbase_Mvc_Controller_ActionController;
+
+class Frontendcontroller extends Tx_Extbase_Mvc_Controller_ActionController
+{
+}

tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassname/MissingNamespaceSniff/nothingTodo/InputFileForIssues.php

@@ -1,7 +1,5 @@
 <?php
 
-namespace Vendor\ExtName\Controller;
-
 /*
  * Copyright (C) 2017  Daniel Siepmann <coding@daniel-siepmann.de>
  *
@@ -23,6 +21,6 @@ namespace Vendor\ExtName\Controller;
 
 use Tx_Extbase_Mvc_Controller_ActionController;
 
-class Frontendcontroller extends Tx_Extbase_Mvc_Controller_ActionController
+class ux_t3lib_DB extends t3lib_DB
 {
 }