If we're going to define _XOPEN_SOURCE, we should at least define it to a

version that includes putenv().  Make it 600 (the current one) for good
measure.

[originally from svn r5048]

unix/pty.c

@@ -11,7 +11,7 @@
  * a null pointer and ignored everywhere.
  */
 
-#define _XOPEN_SOURCE
+#define _XOPEN_SOURCE 600
 #define _XOPEN_SOURCE_EXTENDED
 #define _GNU_SOURCE