Disable _XOPEN_SOURCE for Solaris 2.6. Fixes #690317.

configure

 #! /bin/sh
-# From configure.in Revision: 1.395 .
+# From configure.in Revision: 1.396 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.53 for python 2.3.
 #
@@ -1341,6 +1341,10 @@ case $ac_sys_system/$ac_sys_release in
   # even though select is a POSIX function. Reported by J. Ribbens.
   OpenBSD/2.* | OpenBSD/3.[012])
     define_xopen_source=no;;
+  # On Solaris 2.6, sys/wait.h is inconsistent in the usage
+  # of union __?sigval. Reported by Stuart Bishop.
+  SunOS/5.6)
+    define_xopen_source=no;;
 esac
 
 if test $define_xopen_source = yes

configure.in

@@ -120,6 +120,10 @@ case $ac_sys_system/$ac_sys_release in
   # even though select is a POSIX function. Reported by J. Ribbens.
   OpenBSD/2.* | OpenBSD/3.@<:@012@:>@) 
     define_xopen_source=no;;
+  # On Solaris 2.6, sys/wait.h is inconsistent in the usage
+  # of union __?sigval. Reported by Stuart Bishop.
+  SunOS/5.6)
+    define_xopen_source=no;;
 esac
 
 if test $define_xopen_source = yes