libgc: NDK r11 compatibility (tkill removed)

packages/libgc/pthread_stop_world.c.patch

@@ -0,0 +1,14 @@
+The tkill(2) function was removed from libc in NDK r11.
+
+diff -u -r ../bdwgc-c861ec3d1825b5bb450d20bf9091562fa8a81a4d/pthread_stop_world.c ./pthread_stop_world.c
+--- ../bdwgc-c861ec3d1825b5bb450d20bf9091562fa8a81a4d/pthread_stop_world.c	2016-01-13 03:34:56.000000000 -0500
++++ ./pthread_stop_world.c	2016-03-10 07:09:03.607785056 -0500
+@@ -450,7 +450,7 @@
+ #endif
+ 
+ #ifdef USE_TKILL_ON_ANDROID
+-  extern int tkill(pid_t tid, int sig); /* from sys/linux-unistd.h */
++  static int tkill(pid_t tid, int sig) { return tgkill(-1, tid, sig); }
+ 
+   static int android_thread_kill(pid_t tid, int sig)
+   {