os_support: Define SHUT_RD, SHUT_WR and SHUT_RDWR on OS/2

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

libavformat/os_support.h

@@ -45,6 +45,12 @@ static inline int is_dos_path(const char *path)
     return 0;
 }
 
+#if defined(__OS2__)
+#define SHUT_RD 0
+#define SHUT_WR 1
+#define SHUT_RDWR 2
+#endif
+
 #if defined(_WIN32)
 #define SHUT_RD SD_RECEIVE
 #define SHUT_WR SD_SEND