osx + gcc + WITH_QPBO

[DerThorsten]

Seems like there are some linking/ multiple definitions of problems on os + gcc + WITH_QPBO
when building the qpbo lib

https://travis-ci.org/DerThorsten/nifty/jobs/235373715

[bluescarni]

I noticed that in the QPBO code there are methods of class templates defined in .cpp files, some with inline some not. My suspicion is that the linking problems are related to this.

Is there a specific reason why the code should be split up in .cpp/.hpp for these class templates?

[DerThorsten]

I guess the easiest thing is to turn this into a header only lib.
I can easily do this in my fork