Per Gilles, we really should set the reentrant flags when building Java support

config/ompi_setup_java.m4

@@ -89,6 +89,8 @@ AC_DEFUN([OMPI_SETUP_JAVA_BINDINGS],[
            AC_MSG_WARN([*** the Java MPI bindings in Open MPI is contingent])
            AC_MSG_WARN([*** upon user interest and developer support.])
            AC_MSG_WARN([******************************************************])
+           CFLAGS="$CFLAGS -D_REENTRANT"
+           CPPFLAGS="$CPPFLAGS -D_REENTRANT"
           ])
 
     AC_CONFIG_FILES([