* Maintain integrity of the substitute and successor mappings when

deleting a path in the store.
* Allow absolute paths in Nix expressions.
* Get nix-prefetch-url to work again.
* Various other fixes.

src/libstore/normalise.cc

@@ -82,6 +82,7 @@ Path normaliseStoreExpr(const Path & _nePath, PathSet pending)
             debug(format("skipping build of expression `%1%', someone beat us to it")
 		  % (string) nePath);
             if (ne.type != StoreExpr::neClosure) abort();
+            outputLocks.setDeletion(true);
             return nePath2;
         }
     }