fix INT64_C breakage with ffmpeg

Originally committed to SVN as r967.

aegisub/audio_provider_lavc.cpp

@@ -38,6 +38,15 @@
 // Headers
 #define EMULATE_INTTYPES
 #include <wx/wxprec.h>
+
+/* avcodec.h uses INT64_C in a *single* place. This prolly breaks on Win32,
+ * but, well. Let's at least fix it for Linux.
+ *
+#define __STDC_CONSTANT_MACROS 1
+#include <stdint.h>
+ * - done in posix/defines.h
+ */
+
 #include <ffmpeg/avcodec.h>
 #include <ffmpeg/avformat.h>
 #include "mkv_wrap.h"

aegisub/posix/defines.h

@@ -9,6 +9,7 @@
 #include "acconf.h"
 
 #ifdef HAVE_STDINT_H
+#define __STDC_CONSTANT_MACROS 1
 #include <stdint.h>
 #endif
 #ifdef HAVE_INTTYPES_H