- Add AC_USE_SYSTEM_EXTENSIONS to make autotool...
- Add AC_USE_SYSTEM_EXTENSIONS to make autotool...

- Add AC_USE_SYSTEM_EXTENSIONS to make autotools warnings go away
- Use m4_ifdef, not ifdef

This commit was SVN r4574.

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