Add a test of the type primops

tests/lang/eval-okay-types.exp

@@ -0,0 +1 @@
+[ true false true false true false true false true false "int" "bool" "string" "null" "attrs" "list" "lambda" "lambda" "lambda" "lambda" ]

tests/lang/eval-okay-types.nix

@@ -0,0 +1,23 @@
+with builtins;
+
+[ (isNull null)
+  (isNull (x: x))
+  (isFunction (x: x))
+  (isFunction "fnord")
+  (isString ("foo" + "bar"))
+  (isString [ "x" ])
+  (isInt (1 + 2))
+  (isInt { x = 123; })
+  (isBool (true && false))
+  (isBool null)
+  (typeOf (3 * 4))
+  (typeOf true)
+  (typeOf "xyzzy")
+  (typeOf null)
+  (typeOf { x = 456; })
+  (typeOf [ 1 2 3 ])
+  (typeOf (x: x))
+  (typeOf ((x: y: x) 1))
+  (typeOf map)
+  (typeOf (map (x: x)))
+]