Revert "EditorManager: Fix crash when closing an editor upon activation"

Deleting an editor while currentEditorChanged is apparently not a good
idea.
Use a queued connection instead.

This reverts commits 243a625961,
447c4ed37f,
d9602ca550 and
3103487038.

Change-Id: Iccbee25fb77714963faa6f7184d1f5f53ed348a6
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/cpptools/cppheadersource_test.cpp

@@ -30,7 +30,7 @@
 #include "cpptoolsplugin.h"
 #include "cpptoolsreuse.h"
 
-#include <coreplugin/plugintestutils.h>
+#include <coreplugin/testdatadir.h>
 
 #include <QDir>
 #include <QtTest>
@@ -46,7 +46,7 @@ void CppToolsPlugin::test_headersource()
     QFETCH(QString, headerFileName);
 
     bool wasHeader;
-    Core::Tests::TestDataDir dataDir(
+    Core::Internal::Tests::TestDataDir dataDir(
                 _(SRCDIR "/../../../tests/cppheadersource/") + _(QTest::currentDataTag()));
 
     const QString sourcePath = dataDir.file(sourceFileName);