Honor Qt's naming conventions for m_* prefix in autogenerated setters (dont use 'arg')

The standard for Qt Class member variables is m_variable and the setter, getter and signal is:

public:
  void setVariable(const MyType variable);
  MyType variable() const;
signals:
  void variableChanged();
protected:
  MyType    m_variable;

However the current automatic code generator names variables "arg" for the setter, and eventually you get 'arg's everywhere, this forces to rewrite it as soon as it was auto-generated (makes it less magical less automatic).

Please honor Qt's naming conventions at least when m_* prefix is used:

   void setVariable(const MyType arg); // <- BAD
   void setVariable(const MyType variable); // <- GOOD
protected:
   MyType  m_variable;