Clang: Rename CodeModelBackEnd in ClangBackEnd

Change-Id: I13e8a458634110456375956d4d4da7239c86957f
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/plugins/clangcodemodel/clangcompletion.cpp

@@ -68,7 +68,7 @@
 #include <QTextCursor>
 #include <QTextDocument>
 
-using namespace CodeModelBackEnd;
+using namespace ClangBackEnd;
 using namespace ClangCodeModel;
 using namespace ClangCodeModel::Internal;
 using namespace CPlusPlus;