Doc: Describe the experimental Clang Refactoring plugin

Change-Id: Iad1baf49ae1ad0fde83fdcbdb6c02087af52131a
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

doc/src/editors/creator-editors.qdoc

@@ -1608,6 +1608,10 @@
 
                 \li \uicontrol {Open Documents} searches from all open files.
 
+                \li \uicontrol {Clang Query Project} explores the Clang abstract
+                     syntax tree (AST) using AST matcher expressions. For more
+                     information, see \l{Exploring Clang AST}.
+
             \endlist
 
         \li In the \uicontrol {File pattern} field, specify file patterns to
@@ -1672,6 +1676,34 @@
             \uicontrol {Search engine} field.
 
     \endlist
+
+    \section1 Exploring Clang AST
+
+    You can use the experimental Clang Refactoring plugin to explore the Clang
+    AST using AST matcher expressions. For more information about constructing
+    matcher expressions, see
+    \l {http://clang.llvm.org/docs/LibASTMatchersReference.html}
+    {AST Matcher Reference}.
+
+    To explore the AST:
+
+    \list 1
+
+        \li Select \uicontrol Help > \uicontrol {About Plugins} > \uicontrol C++
+            > \uicontrol {ClangRefactoring} to enable the plugin.
+
+        \li Restart \QC to be able to use the plugin.
+
+        \li When searching, select \uicontrol {Clang Query Project} in the
+            \uicontrol {Scope} field.
+
+        \li Enter an AST matcher expression in the \uicontrol {Search for}
+            field.
+
+    \endlist
+
+    You can view the results of the query as links to code positions in the
+    \uicontrol {Search Results} output pane.
 */