lavc: provide the opt.h header until the next bump

AVOptions were moved to libavutil only recently.

libavcodec/Makefile

@@ -3,7 +3,7 @@ include $(SUBDIR)../config.mak
 NAME = avcodec
 FFLIBS = avutil
 
-HEADERS = avcodec.h avfft.h dxva2.h vaapi.h vdpau.h version.h xvmc.h
+HEADERS = avcodec.h avfft.h dxva2.h opt.h vaapi.h vdpau.h version.h xvmc.h
 
 OBJS = allcodecs.o                                                      \
        audioconvert.o                                                   \

libavcodec/opt.h

+/**
+ * @file
+ * This header is provided for compatibility only and will be removed
+ * on next major bump
+ */
+
+#ifndef AVCODEC_OPT_H
+#define AVCODEC_OPT_H
+
+#include "libavcodec/version.h"
+
+#if FF_API_OPT_H
+#include "libavutil/opt.h"
+#endif
+
+#endif

libavcodec/version.h

@@ -62,5 +62,8 @@
 #ifndef FF_API_REQUEST_CHANNELS
 #define FF_API_REQUEST_CHANNELS (LIBAVCODEC_VERSION_MAJOR < 54)
 #endif
+#ifndef FF_API_OPT_H
+#define FF_API_OPT_H            (LIBAVCODEC_VERSION_MAJOR < 54)
+#endif
 
 #endif /* AVCODEC_VERSION_H */