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>

tests/unit/unittest/data/query_simpleclass.cpp

@@ -0,0 +1,8 @@
+class Class
+{
+public:
+    int x;
+
+
+
+};