Clang: Add clang query

Clang query is mechanism to use AST matcher to search for code. Think
about regular expression but in the context of AST. So you get a semantic
search tool for C++.

Change-Id: I72e882c5b53a0c52f352a3664847c4c3e4f6fc2e
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/libs/clangbackendipc/refactoringserverproxy.h

@@ -51,6 +51,7 @@ public:
 
     void end() override;
     void requestSourceLocationsForRenamingMessage(ClangBackEnd::RequestSourceLocationsForRenamingMessage &&message) override;
+    void requestSourceRangesAndDiagnosticsForQueryMessage(RequestSourceRangesAndDiagnosticsForQueryMessage &&message);
 
     void readMessages();