Remove backward-compatible implementations of some primops

Nixpkgs requires at least Nix 1.2 anyway, so these are now useless.

lib/attrsets.nix

@@ -20,7 +20,7 @@ rec {
     let attr = head attrPath;
     in
       if attrPath == [] then e
-      else if builtins ? hasAttr && hasAttr attr e
+      else if hasAttr attr e
       then attrByPath (tail attrPath) default (getAttr attr e)
       else default;
 
@@ -110,7 +110,7 @@ rec {
   collect = pred: attrs:
     if pred attrs then
       [ attrs ]
-    else if builtins.isAttrs attrs then
+    else if isAttrs attrs then
       concatMap (collect pred) (attrValues attrs)
     else
       [];

lib/lists.nix

@@ -10,7 +10,7 @@ let
 
 in rec {
 
-  inherit (builtins) head tail length isList elemAt;
+  inherit (builtins) head tail length isList elemAt concatLists filter elem;
 
 
   # Create a list consisting of a single element.  `singleton x' is
@@ -58,10 +58,6 @@ in rec {
     in imap' 0;
 
 
-  # Concatenate a list of lists.
-  concatLists = builtins.concatLists or (fold (x: y: x ++ y) []);
-
-
   # Map and concatenate the result.
   concatMap = f: list: concatLists (map f list);
 
@@ -75,24 +71,10 @@ in rec {
     else [x];
 
 
-  # Filter a list using a predicate; that is, return a list containing
-  # every element from `list' for which `pred' returns true.
-  filter =
-    builtins.filter or
-    (pred: list:
-      fold (x: y: if pred x then [x] ++ y else y) [] list);
-
-
   # Remove elements equal to 'e' from a list.  Useful for buildInputs.
   remove = e: filter (x: x != e);
 
 
-  # Return true if `list' has an element `x'.
-  elem =
-    builtins.elem or
-    (x: list: fold (a: bs: x == a || bs) false list);
-
-
   # Find the sole element in the list matching the specified
   # predicate, returns `default' if no such element exists, or
   # `multiple' if there are multiple matching elements.