lavf: move avio_enum_protocols() to protocols.c

It's a more appropriate place for it.

libavformat/avio.c

@@ -79,21 +79,6 @@ const AVClass ffurl_context_class = {
 };
 /*@}*/
 
-const char *avio_enum_protocols(void **opaque, int output)
-{
-    const URLProtocol **p = *opaque;
-
-    p = p ? p + 1 : ff_url_protocols;
-    *opaque = p;
-    if (!*p) {
-        *opaque = NULL;
-        return NULL;
-    }
-    if ((output && (*p)->url_write) || (!output && (*p)->url_read))
-        return (*p)->name;
-    return avio_enum_protocols(opaque, output);
-}
-
 static int url_alloc_for_protocol(URLContext **puc, const URLProtocol *up,
                                   const char *filename, int flags,
                                   const AVIOInterruptCB *int_cb)

libavformat/protocols.c

@@ -162,3 +162,18 @@ const URLProtocol *ff_url_protocols[] = {
 #endif
     NULL,
 };
+
+const char *avio_enum_protocols(void **opaque, int output)
+{
+    const URLProtocol **p = *opaque;
+
+    p = p ? p + 1 : ff_url_protocols;
+    *opaque = p;
+    if (!*p) {
+        *opaque = NULL;
+        return NULL;
+    }
+    if ((output && (*p)->url_write) || (!output && (*p)->url_read))
+        return (*p)->name;
+    return avio_enum_protocols(opaque, output);
+}