Permission: add option "host_permissions"

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1115

src/Permission.hxx

@@ -23,6 +23,7 @@
 #include "config.h"
 
 struct ConfigData;
+class SocketAddress;
 
 static constexpr unsigned PERMISSION_NONE = 0;
 static constexpr unsigned PERMISSION_READ = 1;
@@ -45,6 +46,12 @@ unsigned
 GetLocalPermissions() noexcept;
 #endif
 
+#ifdef HAVE_TCP
+[[gnu::pure]]
+int
+GetPermissionsFromAddress(SocketAddress address) noexcept;
+#endif
+
 void
 initPermissions(const ConfigData &config);