avio: Add an URLProtocol flag for indicating that a protocol uses network

This definition is in two files, since the definitions will move
to the private header at the next bump.

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

libavformat/avio.h

@@ -146,6 +146,7 @@ typedef struct URLContext {
 } URLContext;
 
 #define URL_PROTOCOL_FLAG_NESTED_SCHEME 1 /*< The protocol name can be the first part of a nested protocol scheme */
+#define URL_PROTOCOL_FLAG_NETWORK       2 /*< The protocol uses network */
 
 /**
  * @deprecated This struct is to be made private. Use the higher-level