Clang: Fix reloading documents

Fix the following use case:
 * Open foo.h
 * Open foo.cpp
 * Change both files externally (e.g. git checkout) e.g. by adding a
   function (declaration + definition)
 * Confirm the reload dialog in Qt Creator
 * The added function in foo.cpp gets a diagnostic that it's out of line
   although foo.h is also reloaded.

TextDocument::contentsChangedWithPosition() is also emitted during a
reload. However, the revision of the document at that point is not yet
updated. This led to an out-dated copy of the unsaved files in the clang
backend.

Change-Id: I70580d32bb7a34dc43356dc05019cc18addf950e
Reviewed-by: Marco Bubke <marco.bubke@theqtcompany.com>

src/plugins/clangcodemodel/clangmodelmanagersupport.h

@@ -72,10 +72,12 @@ public:
 private:
     void onEditorOpened(Core::IEditor *editor);
     void onCurrentEditorChanged(Core::IEditor *newCurrent);
+    void onCppDocumentAboutToReloadOnTranslationUnit();
     void onCppDocumentReloadFinishedOnTranslationUnit(bool success);
     void onCppDocumentContentsChangedOnTranslationUnit(int position,
                                                        int charsRemoved,
                                                        int charsAdded);
+    void onCppDocumentAboutToReloadOnUnsavedFile();
     void onCppDocumentReloadFinishedOnUnsavedFile(bool success);
     void onCppDocumentContentsChangedOnUnsavedFile();
 
@@ -93,6 +95,9 @@ private:
 
     void connectTextDocumentToTranslationUnit(TextEditor::TextDocument *textDocument);
     void connectTextDocumentToUnsavedFiles(TextEditor::TextDocument *textDocument);
+    void connectToTextDocumentContentsChangedForTranslationUnit(
+            TextEditor::TextDocument *textDocument);
+    void connectToTextDocumentContentsChangedForUnsavedFile(TextEditor::TextDocument *textDocument);
     void connectToWidgetsMarkContextMenuRequested(QWidget *editorWidget);
 
 private: