Merge branch 'develop' into openfoam4

* develop: (200 commits)
  Drop comments about X11, moved to #3519
  Add warning about Tk and X
  Still allow Tk but add comment
  Bring libxml2/2.9.4 with Python in sync with the others
  add easyconfig gperftools-2.5-intel-2016b.eb
  add easyconfig gperftools-2.5-intel-2016b.eb, add easyconfig libunwind-1.1-intel-2016b.eb
  Circos 0.69-2 using ictce 5.5.0 toolchain
  clean up libxml2 easyconfigs according to updated libxml2 easyblock
  Add comment in patch about it's purpose
  Add CMake/3.6.1 for intel/2016b
  Use libxml2 easyblock for Python
  Don't build Tkinter in Python as it requires X11
  Use EB python in libxml2
  Add python enabled libxml2 for Mesa
  Downgrade to build deps
  Correct versionsuffix
  Updated Mesa deps
  Added deps for Mesa
  Fix easyconfig location
  Added Mesa/12.0.1 for intel/2016b
  ...