Quiet the noisy "already defined" warning triggered, when building with TCL_THREADS.

--- ../unix/tclUnixPort.h	Tue Dec  6 04:01:07 2005
+++ ../unix/tclUnixPort.h	Tue Jun 27 15:16:21 2006
@@ -607,4 +607,7 @@
 #endif
 EXTERN char *          	TclpInetNtoa(struct in_addr);
+#ifdef inet_ntoa
+#	undef inet_ntoa
+#endif
 #define inet_ntoa(x)	TclpInetNtoa(x)
 #else