dshow: handle events in graph

Handling DirectShow events prevents infinite loops when there is an error in
the graph, such as a device being disconnected. This makes it possible for
dshow to return an error to the caller and run the cleanup code.

Based on patch by Don Moir <donmoir@comcast.net>.

libavdevice/dshow_capture.h

@@ -32,6 +32,11 @@
 #include <dshow.h>
 #include <dvdmedia.h>
 
+/* EC_DEVICE_LOST is not defined in MinGW dshow headers. */
+#ifndef EC_DEVICE_LOST
+#define EC_DEVICE_LOST 0x1f
+#endif
+
 long ff_copy_dshow_media_type(AM_MEDIA_TYPE *dst, const AM_MEDIA_TYPE *src);
 void ff_print_VIDEO_STREAM_CONFIG_CAPS(const VIDEO_STREAM_CONFIG_CAPS *caps);
 void ff_print_AUDIO_STREAM_CONFIG_CAPS(const AUDIO_STREAM_CONFIG_CAPS *caps);