* Allow unprivileged users to do `nix-store --clear-failed-paths' and

`nix-store --query-failed-paths'.

src/libstore/worker-protocol.hh

@@ -36,6 +36,8 @@ typedef enum {
     wopQuerySubstitutablePathInfo = 21,
     wopQueryDerivationOutputs = 22,
     wopQueryValidPaths = 23,
+    wopQueryFailedPaths = 24,
+    wopClearFailedPaths = 25,
 } WorkerOp;