Implemented tests for Toy_Parser

The parser now correctly produces a workable AST. I think I'll skip
over the optimizer, and begin on the compiler next session. The
optimizer will act directly on the AST, but it isn't totally necessary.

Other tools can also operate on the AST, such as for debugging - I'll
have to ask what kinds are out there.

source/toy_ast.c

@@ -82,3 +82,9 @@ void Toy_private_emitAstError(Toy_Bucket** bucket, Toy_Ast** handle) {
 
 	(*handle)->error.type = TOY_AST_ERROR;
 }
+
+void Toy_private_emitAstEnd(Toy_Bucket** bucket, Toy_Ast** handle) {
+	(*handle) = (Toy_Ast*)Toy_partBucket(bucket, sizeof(Toy_Ast));
+
+	(*handle)->error.type = TOY_AST_END;
+}