liburcu: add patch to fix build with uClibc

Under uClibc, defining _GNU_SOURCE is strictly needed to access the
CPU_*() macros.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/liburcu/liburcu-0.6.7-missing-gnu-source.patch

@@ -0,0 +1,13 @@
+Define _GNU_SOURCE to access CPU_ZERO() macro in uClibc
+
+Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+
+Index: userspace-rcu-0.6.7/tests/urcutorture.c
+===================================================================
+--- userspace-rcu-0.6.7.orig/tests/urcutorture.c	2012-02-01 10:17:09.938804402 +0100
++++ userspace-rcu-0.6.7/tests/urcutorture.c	2012-02-01 10:17:15.308713372 +0100
+@@ -1,3 +1,4 @@
++#define _GNU_SOURCE
+ #include <string.h>
+ #include <sys/time.h>
+ #include <poll.h>