Add regression tests

Added regression tests as asked by @joemfb to test that currying and composition gates strip faces and that the subject of a gate returned by ++curr nests under the head of curried gate's subject.

tests/sys/hoon/func.hoon

@@ -0,0 +1,23 @@
+::  Tests for currying gates and ++corl
+::
+/+  *test
+|%
+++  test-func
+  ;:  weld
+    %+  expect-eq
+      !>  `(list)`~[0 1 2]
+      !>  ((curr oust `(list)`~[0 1 2]))
+    %+  expect-eq
+      !>  `@`6
+      !>  ((curr roll add) (gulf 1 3))
+    %+  expect-eq
+      !>  `@`6
+      !>  ((cury roll (gulf 1 3)) add)
+    ::  check that ++corl strips face from b's subject
+    ::
+    %+  expect-eq
+      !>  `@`15
+      !>  ((corl same (cury roll (gulf 1 5))) add)
+  ==
+::
+--