fix tr1 header enable/disable switch, fixes FS#458, merge to r1.2

[[Imported from SVN: r5426]]

m4/dune_common.m4

@@ -42,17 +42,19 @@ AC_DEFUN([DUNE_COMMON_CHECKS],
   dnl checks for header files.
   AC_REQUIRE([AC_HEADER_STDC])
   AC_LANG_PUSH([C++])
+
+  AC_CHECK_HEADERS([malloc.h string.h])
+
   # Allow disabling tr1 headers. E.g. needed for broken xlc on Blue Gene
   AC_ARG_ENABLE(tr1-headers, 
 	AC_HELP_STRING([--disable-tr1-headers], 
 	[Prevents checking for  tr1 headers like tuple, array, etc. 
 	This might be needed for broken compilers like xlc on Blue Gene]), 
-	[], [enable_tr1_headers=yes])
-
-  if test "x$enable_tr1_headers" = "xyes" ; then
-    tr1_headers="type_traits tr1/type_traits array tr1/array tuple tr1/tuple"
-  fi
-  AC_CHECK_HEADERS([malloc.h string.h $tr1_headers])
+	[], [    
+	  AC_CHECK_HEADERS([type_traits tr1/type_traits
+                        array tr1/array tuple tr1/tuple])
+	  ])
+  
   AC_LANG_POP([C++])
 
   dnl checks for typedefs, structures, and compiler characteristics.