Log Message:
Update to hwloc-1.7.1

Changes since 1.7 from NEWS file:

Version 1.7.1
-------------
* Fix a failed assertion in the distance grouping code when loading a XML
  file that already contains some groups.
  Thanks to Laercio Lima Pilla for reporting the problem.
* Remove unexpected Group objects when loading XML topologies with I/O
  objects and NUMA distances.
  Thanks to Elena Elkina for reporting the problem and testing patches.
* Fix PCI link speed discovery when using libpciaccess.
* Fix invalid libpciaccess virtual function device/vendor IDs when using
  SR-IOV PCI devices on Linux.
* Fix GL component build with old NVCtrl releases.
  Thanks to Jirka Hladky for reporting the problem.
* Fix embedding breakage caused by libltdl.
  Thanks to Pavan Balaji for reporting the problem.
* Always use the system-wide libltdl instead of shipping one inside hwloc.
* Document issues when enabling plugins while embedding hwloc in another
  project, in the documentation section Embedding hwloc in Other Software.
* Add a FAQ entry "How to get useful topology information on NetBSD?"
  in the documentation.
* Somes fixes in the renaming code for embedding.
* Miscellaneous minor build fixes.