Enable generic index creation and seeking for NUV demuxer.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17966 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/nuv.c

@@ -259,4 +259,5 @@ AVInputFormat nuv_demuxer = {
     nuv_packet,
     NULL,
     NULL,
+    .flags = AVFMT_GENERIC_INDEX,
 };