protect shell code from m4 substitution

[[Imported from SVN: r5118]]

m4/dune.m4

@@ -220,7 +220,7 @@ AC_DEFUN([DUNE_CHECK_MODULES],[
   if test "x$_DUNE_MODULE[]_VERSION" != "x"; then
 	txt="$txt version $_DUNE_MODULE[]_VERSION"
   fi
-  DUNE_SUMMARY="$DUNE_SUMMARY echo '$txt';"
+  [DUNE_SUMMARY="$DUNE_SUMMARY echo '$txt';"]
 
   # remove local variables
   m4_popdef([_dune_name])

m4/dune_all.m4

@@ -165,7 +165,7 @@ AC_DEFUN([DUNE_SUMMARY_ALL],[
   echo
   echo "-----------------------------"
   echo  
-  eval $DUNE_SUMMARY
+  [eval $DUNE_SUMMARY]
   echo "ALBERTA..........: $with_alberta"
   echo "ALUGrid..........: $with_alugrid"
   echo "AmiraMesh........: $with_amiramesh"