awk: when parsing length(), simplify eating of LPAREN

function                                             old     new   delta
parse_expr                                           945     948      +3

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/editors/awk.c b/editors/awk.c
index 6833c2f..f65449a 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -1453,10 +1453,11 @@
 				| TC_BINOPX    /* length <op> NUM */
 				| TC_COMMA     /* print length, 1 */
 			);
-			rollback_token();
-			if (tc & TC_LPAREN) {
+			if (tc != TC_LPAREN)
+				rollback_token();
+			else {
 				/* It was a "(" token. Handle just like TC_BUILTIN */
-				cn->l.n = parse_lrparen_list();
+				cn->l.n = parse_expr(TC_RPAREN);
 			}
 			break;
 		}