Protect hwloc/configure/m4's use of some temporary shell variables

Fix problem reported by Paul Hargrove:
http://www.open-mpi.org/community/lists/devel/2013/12/13519.php

cmr=v1.7.4:reviewer=brbarret

This commit was SVN r30013.

opal/mca/hwloc/configure.m4

@@ -120,6 +120,7 @@ AC_DEFUN([MCA_opal_hwloc_CONFIG_REQUIRE],[
         # Otherwise, if we try to AC RUN_IFELSE anything here in
         # configure, it might die because it can't find the libraries
         # we just linked against.
+        OPAL_VAR_SCOPE_PUSH([found_l token tmp dir])
         found_l=0
         eval "tmp=\$opal_hwloc_${opal_hwloc_winner}_ADD_LIBS"
         for token in $tmp; do
@@ -138,6 +139,7 @@ AC_DEFUN([MCA_opal_hwloc_CONFIG_REQUIRE],[
                        ;;
                    esac
                done])
+        OPAL_VAR_SCOPE_POP
     ])
 
     AM_CONDITIONAL(OPAL_HAVE_HWLOC, test $OPAL_HAVE_HWLOC -eq 1)