valgrind: added patch to make this build with recent kernel-libc-headers.

srcpkgs/valgrind/patches/use-sys-pthread-header.patch

@@ -0,0 +1,10 @@
+--- coregrind/vgdb.c.orig	2013-08-13 11:47:04.267748406 +0200
++++ coregrind/vgdb.c	2013-08-13 11:47:11.851818772 +0200
+@@ -102,7 +102,6 @@ I_die_here : (PTRACEINVOKER) architectur
+ #include <sys/user.h>
+ #if defined(VGO_linux)
+ #  include <sys/prctl.h>
+-#  include <linux/ptrace.h>
+ #endif
+ #endif
+