Function av_buffer_pool_init2

pub unsafe extern "C" fn av_buffer_pool_init2(
    size: usize,
    opaque: *mut c_void,
    alloc: Option<unsafe extern "C" fn(*mut c_void, usize) -> *mut AVBufferRef>,
    pool_free: Option<unsafe extern "C" fn(*mut c_void)>,
) -> *mut AVBufferPool