removed warning

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2016 c046a42c-6fe2-441c-8c8c-71466251a162

osdep.h

@@ -27,6 +27,8 @@ extern void __longjmp(jmp_buf env, int val);
 
 #include <signal.h>
 
+struct siginfo;
+
 /* NOTE: it works only because the glibc sigset_t is >= kernel sigset_t */
 struct qemu_sigaction {
     union {