Disable _XOPEN_SOURCE for Solaris 2.6. Fixes #690317.
diff --git a/configure.in b/configure.in
index 586e60a..ed1ee95 100644
--- a/configure.in
+++ b/configure.in
@@ -120,6 +120,10 @@
   # 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