Clang: Simplify triggering initialization of supportive translation unit

Use a flag to indicate whether a supportive translation unit should be
set up. It will be needed in a follow-up change, too.

Change-Id: I6858caa303fcd9dca9486607380240dd5895a14a
Reviewed-by: David Schulz <david.schulz@qt.io>

src/tools/clangbackend/ipcsource/clangdocument.h

@@ -90,6 +90,10 @@ public:
     uint documentRevision() const;
     void setDocumentRevision(uint revision);
 
+    bool isResponsivenessIncreased() const;
+    bool isResponsivenessIncreaseNeeded() const;
+    void setResponsivenessIncreaseNeeded(bool responsivenessIncreaseNeeded);
+
     bool isUsedByCurrentEditor() const;
     void setIsUsedByCurrentEditor(bool isUsedByCurrentEditor);