Fix false positive for AIO on OpenBSD

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6343 c046a42c-6fe2-441c-8c8c-71466251a162

configure

@@ -1005,7 +1005,9 @@ if test "$aio" = "yes" ; then
   aio=no
   cat > $TMPC << EOF
 #include <pthread.h>
-int main(void) { pthread_mutex_t lock; return 0; }
+#include <signal.h>
+int main(void) { struct sigevent s; pthread_mutex_t lock;
+    return sigqueue(0, 0, s.sigev_value); }
 EOF
   if $cc $ARCH_CFLAGS -o $TMPE $AIOLIBS $TMPC 2> /dev/null ; then
     aio=yes