Use HAVE_STRINGS_H instead of WIN32 in r26728.

This commit was SVN r26729.

The following SVN revision numbers were found above:
  r26728 --> open-mpi/ompi@c97f46bcc7

opal/mca/hwloc/hwloc142/hwloc/src/topology-synthetic.c

@@ -14,7 +14,7 @@
 
 #include <limits.h>
 #include <assert.h>
-#ifndef _WIN32
+#ifdef HAVE_STRINGS_H
 #include <strings.h>
 #endif
 

opal/mca/hwloc/hwloc142/hwloc/src/topology-xml.c

@@ -13,7 +13,7 @@
 #include <private/debug.h>
 
 #include <assert.h>
-#ifndef _WIN32
+#ifdef HAVE_STRINGS_H
 #include <strings.h>
 #endif