Make the "Show symbols" option of the module window work on Windows.

Introduce API to debug engines and debugger manager to do this.
Reviewed-by: hjk <qtc-commiter@nokia.com>

src/plugins/debugger/scriptengine.h

@@ -102,6 +102,7 @@ private:
 
     void loadSymbols(const QString &moduleName);
     void loadAllSymbols();
+    virtual QList<Symbol> moduleSymbols(const QString &moduleName);
     void reloadDisassembler();
     void reloadModules();
     void reloadRegisters() {}