message: fixed doc make issue on Ubuntu
diff: +SHELL := /bin/bash
  +
  webpages := $(addprefix www/, $(addsuffix .html, index news demos documentation gallery downloads related_projects pvospray displaywall fiu_comparison legal))
  process_version := $(addprefix tmp/, $(addsuffix .md, demos getting_ospray readme_head))
  tmptexfiles := $(addprefix tmp/, $(addsuffix .tex, overview changelog compilation api mpi scenegraph examples))
  