lupdate needs support for objective c++

Using qtconnectivity as example, the way to update the ts files is to run

make ts-qtconnectivity-de

This make target completely fails to parse *.mm files. This can be seen when checking for tr strings which are unique to .mm files. This means i18n is completely insufficient for ios and OSX.

It seems lupdate has an -extensions option which might be used to fix the problem. If the option is not set it defaults to

'java,jui,ui,c,c++,cc,cpp,cxx,ch,h,h++,hh,hpp,hxx,js,qs,qml'

It could be just a matter of adding .mm as default extension. However whether lupdate is able to parse proper Objective-C is another problem.