Fix typo reported by Thiemo Seufer

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5782 c046a42c-6fe2-441c-8c8c-71466251a162

configure

@@ -148,7 +148,7 @@ FreeBSD)
 bsd="yes"
 audio_drv_list="oss"
 audio_possible_drivers="oss sdl esd pa"
-aiolib="-lpthread"
+aio_lib="-lpthread"
 if [ "$cpu" = "i386" -o "$cpu" = "x86_64" ] ; then
     kqemu="yes"
 fi