Add identifier name for side condition. (#4902)

```
(! sc (^ ...)
      ^ this is the identifier!
```

We require that side-conditions have an identifier. We usually provide
this identifier, but in this one case we did not.

The old lexer accepted the side condition without the identifier. The
new one does not.

diff --git a/test/signatures/drat_test.plf b/test/signatures/drat_test.plf
index e5335a6bb067712bc79b2abb228229fab979829d..d66e48f8d23bd2110ee6da6ad9205020a245f39c 100644 (file)
--- a/test/signatures/drat_test.plf
+++ b/test/signatures/drat_test.plf
@@ -6,7 +6,7 @@
          (! a clause
             (! b clause
                (! result bool
-                  (! (^
+                  (! sc (^
                        (bool_and
                            (bool_eq (clause_eq a b) result)
                        (bool_and