Debugger: Add incremental API for modules.

And use it from CDB's module load/unload callbacks
instead of re-setting all modules. Some cleanup.
Acked-by: hjk

src/plugins/debugger/moduleshandler.h

@@ -101,6 +101,9 @@ public:
     QAbstractItemModel *model() const;
 
     void setModules(const QList<Module> &modules);
+    void addModule(const Module &module);
+    void removeModule(const QString &moduleName);
+
     QList<Module> modules() const;
     void removeAll();