Make AVOptionType a bitfield/int wrapper (#57)

* Implement option::Type as bitfield struct

This type is no longer strictly an enum in the
Rust sense because the underlying AVOptionType
is now also a bitfield/the AV_OPT_TYPE* consts
now include AV_OPT_TYPE_FLAG_ARRAY, which is a
bitflag.

ffmpeg-sys-the-third/build.rs

@@ -1045,6 +1045,9 @@ fn main() {
         // We need/want to implement Debug by hand for some types
         .no_debug("AVChannelLayout")
         .no_debug("AVChannelCustom")
+        // In FFmpeg 7.0+, this has bitfield-like behaviour,
+        // so cannot be a "rustified" enum
+        .newtype_enum("AVOptionType")
         .allowlist_file(r#".*[/\\]libavutil[/\\].*"#)
         .allowlist_file(r#".*[/\\]libavcodec[/\\].*"#)
         .allowlist_file(r#".*[/\\]libavformat[/\\].*"#)