decoder/Thread: reimplement HasRemoteTagScanner() using the InputPlugin list

src/input/Registry.hxx

@@ -21,6 +21,7 @@
 #define MPD_INPUT_REGISTRY_HXX
 
 #include "check.h"
+#include "util/Compiler.h"
 
 /**
  * NULL terminated list of all input plugins which were enabled at
@@ -40,4 +41,8 @@ extern bool input_plugins_enabled[];
 	input_plugins_for_each(plugin) \
 		if (input_plugins_enabled[input_plugin_iterator - input_plugins])
 
+gcc_pure
+bool
+HasRemoteTagScanner(const char *uri) noexcept;
+
 #endif