Clang fixes related to Boost Serialization

The following fixes a few errors reported by Clang and seen by Boost Serialization script.
+1


> In CalibFormats/SiPixelObjects/interface/PixelCalibConfiguration.h:
>
> > @@ -174,7 +174,7 @@ namespace pos{
> >
> >      virtual void writeASCII(std::string dir="") const;
> >      void 	 writeXML(        pos::PixelConfigKey key, int version, std::string path) const {;}
> > -    virtual void writeXMLHeader(  pos::PixelConfigKey key,
> > +    virtual void writeXMLHeader(  pos::PixelConfigKey &key,
>
> I thought something similar. But when again this would be hiding
> overloaded function, I think. If that should be done on a base class are
> lot more classes would need to be modified, but that would fix quite a
> number of Clang errors/warnings. There are a lot more files having exact
> same issue, mis-matching signature and then hiding overloaded method.
>
>
ah, sorry, did not check for that. agreed then - until we have the time to
attack the base-class and all it's usages. :(

Thanks,
       cheers, andreas