removed warning


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2016 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/osdep.h b/osdep.h
index f818ce0..29a261c 100644
--- a/osdep.h
+++ b/osdep.h
@@ -27,6 +27,8 @@
 
 #include <signal.h>
 
+struct siginfo;
+
 /* NOTE: it works only because the glibc sigset_t is >= kernel sigset_t */
 struct qemu_sigaction {
     union {