fftools: Check HAVE_GETSTDHANDLE before using GetStdHandle

GetStdHandle is unavailable outside of the desktop API subset.

This didn't use to be a problem with earlier WinSDKs, as kbhit also
used to be available only for desktop apps, and this whole section is
wrapped in #if HAVE_KBHIT. With newer WinSDKs, kbhit() is available also
for non-desktop apps, while GetStdHandle still isn't.

Signed-off-by: Martin Storsjö <martin@martin.st>

fftools/ffmpeg.c

@@ -308,7 +308,7 @@ static int read_key(void)
         return n;
     }
 #elif HAVE_KBHIT
-#    if HAVE_PEEKNAMEDPIPE
+#    if HAVE_PEEKNAMEDPIPE && HAVE_GETSTDHANDLE
     static int is_pipe;
     static HANDLE input_handle;
     DWORD dw, nchars;