Fix libnut/ffmpeg compilation on i686-pc-mingw32

Fixes #255.

Signed-off-by: Timothy Gu <timothygu99@gmail.com>

src/libnut-1-fix-ftello.patch

@@ -0,0 +1,15 @@
+diff --git a/libnut/priv.h b/libnut/priv.h
+index 5183503..aac2952 100644
+--- a/libnut/priv.h
++++ b/libnut/priv.h
+@@ -44,6 +44,10 @@
+ #define MAX(a,b) ((a) > (b) ? (a) : (b))
+ #define ABS(a) ((a) > 0 ? (a) : -(a))
+ 
++#if (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR))
++#define ftello(a) (off_t)(_ftelli64(a))
++#endif
++
+ typedef struct {
+ 	nut_input_stream_tt isc;
+ 	int is_mem;