lib.trivial: Remove unneeded polyfills

Nix 2.3 (the minimum version needed to evaluate Nixpkgs) supports these, so no need to keep them around.

lib/trivial.nix

@@ -95,21 +95,6 @@ in {
   /* boolean “and” */
   and = x: y: x && y;
 
-  /* bitwise “and” */
-  bitAnd = builtins.bitAnd
-    or (import ./zip-int-bits.nix
-        (a: b: if a==1 && b==1 then 1 else 0));
-
-  /* bitwise “or” */
-  bitOr = builtins.bitOr
-    or (import ./zip-int-bits.nix
-        (a: b: if a==1 || b==1 then 1 else 0));
-
-  /* bitwise “xor” */
-  bitXor = builtins.bitXor
-    or (import ./zip-int-bits.nix
-        (a: b: if a!=b then 1 else 0));
-
   /* bitwise “not” */
   bitNot = builtins.sub (-1);
 
@@ -165,8 +150,8 @@ in {
   inherit (builtins)
     pathExists readFile isBool
     isInt isFloat add sub lessThan
-    seq deepSeq genericClosure;
-
+    seq deepSeq genericClosure
+    bitAnd bitOr bitXor;
 
   ## nixpkgs version strings