linux: isolate and document backend callbacks f...
linux: isolate and document backend callbacks f...

linux: isolate and document backend callbacks function section better

This commit was SVN r5327.

shekkbuilder/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,ggouaillardet/hwloc