avdevice/decklink: add support for setting duplex mode

This patch also makes BlackMagic drivers v10.6.1 a hard requirement.

Reviewed-by: Deti Fliegl <deti@fliegl.de>
Signed-off-by: Marton Balint <cus@passwd.hu>

libavdevice/decklink_common.h

@@ -44,6 +44,8 @@ struct decklink_ctx {
     IDeckLink *dl;
     IDeckLinkOutput *dlo;
     IDeckLinkInput *dli;
+    IDeckLinkConfiguration *cfg;
+    IDeckLinkAttributes *attr;
     decklink_output_callback *output_callback;
     decklink_input_callback *input_callback;
 
@@ -77,6 +79,7 @@ struct decklink_ctx {
     int list_formats;
     int64_t teletext_lines;
     double preroll;
+    int duplex_mode;
 
     int frames_preroll;
     int frames_buffer;