Fix utterly broken selector chain search code.
Fix utterly broken selector chain search code.

svn path=/trunk/libcss/; revision=8604

zhuyadong/libcss,servo/libcss,servo/libcss,prepare/netsurf_libcss,prepare/netsurf_libcss,prepare/netsurf_libcss,zhuyadong/libcss,zhuyadong/libcss,servo/libcss