Merge commit 'ab56fabe'

* commit 'ab56fabe':
  vfwcap: Add fallback define for HWND_MESSAGE

The merged commit reverts the HWND_MESSAGE removial, and adds a #ifndef around
    commit 8bc52dbd
        vfwcap: Drop fallback VfW defines
        The defines were added long ago when MinGW still lacked them.
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavdevice/vfwcap.c

@@ -27,6 +27,11 @@
 #include <vfw.h>
 #include "avdevice.h"
 
+/* Some obsolete versions of MinGW32 before 4.0.0 lack this. */
+#ifndef HWND_MESSAGE
+#define HWND_MESSAGE ((HWND) -3)
+#endif
+
 struct vfw_ctx {
     const AVClass *class;
     HWND hwnd;