blame the caller for the memory allocated by
strdup.

Reference: /n/sources/patch/applied/strduptag
Date: Mon Jul  7 17:38:21 CES 2008
Signed-off-by: quanstro@quanstro.net

--- /sys/src/libc/port/strdup.c	Mon Jul  7 17:37:53 2008
+++ /sys/src/libc/port/strdup.c	Mon Jul  7 17:37:52 2008
@@ -9,6 +9,6 @@
 	ns = malloc(strlen(s) + 1);
 	if(ns == 0)
 		return 0;
-
+	setmalloctag(ns, getcallerpc(&s));
 	return strcpy(ns, s);
 }