SystemTopology: add support for hwloc 2.0
This is needed to build on OSX using Homebrew using generic.cfg if hwloc from HomeBrew is installed (which is [version 2](https://formulae.brew.sh/formula/hwloc)).
This fixes issue #2129
Unless objections are raised, I will apply this after March 13th.
This is needed to build on OSX using Homebrew using generic.cfg if hwloc from HomeBrew is installed (which is [version 2](https://formulae.brew.sh/formula/hwloc)).
This fixes issue #2129
Unless objections are raised, I will apply this after March 13th.