Clang: new empty locator filter classes

Introduce classes to replace builtin locator filters.

Change-Id: I5cc6f15fb0f59ea8a51b14a86301cf219cc0d6d6
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/clangcodemodel/clangmodelmanagersupport.cpp

@@ -31,6 +31,7 @@
 #include "clangfollowsymbol.h"
 #include "clanghoverhandler.h"
 #include "clangrefactoringengine.h"
+#include "clangcurrentdocumentfilter.h"
 
 #include <coreplugin/editormanager/editormanager.h>
 #include <cpptools/cppfollowsymbolundercursor.h>