Fix libavformat version extraction in configure

This fixes shared library builds broken by
50196a982bf7c8be9b41053fa0975473c217e709

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 4ad66441c9fdd2d33d59e36a897a45828f3062f3)

diff --git a/configure b/configure
index 0f5a6ab..001f00a 100755 (executable)
--- a/configure
+++ b/configure
@@ -3244,7 +3244,7 @@ get_version LIBPOSTPROC libpostproc/postprocess.h
 get_version LIBAVCODEC  libavcodec/avcodec.h
 get_version LIBAVCORE   libavcore/avcore.h
 get_version LIBAVDEVICE libavdevice/avdevice.h
-get_version LIBAVFORMAT libavformat/avformat.h
+get_version LIBAVFORMAT libavformat/version.h
 get_version LIBAVUTIL   libavutil/avutil.h
 get_version LIBAVFILTER libavfilter/avfilter.h