patch 8.2.1378: cannot put space between function name and paren

Problem:    Cannot put space between function name and paren.
Solution:   Allow this for backwards compatibility.
diff --git a/src/eval.c b/src/eval.c
index a7f6086..877b3bc 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3198,9 +3198,12 @@
 	{
 	    int	    flags = evalarg == NULL ? 0 : evalarg->eval_flags;
 
-	    if (**arg == '(')
+	    if ((in_vim9script() ? **arg : *skipwhite(*arg)) == '(')
+	    {
 		// "name(..."  recursive!
+		*arg = skipwhite(*arg);
 		ret = eval_func(arg, evalarg, s, len, rettv, flags, NULL);
+	    }
 	    else if (flags & EVAL_CONSTANT)
 		ret = FAIL;
 	    else if (evaluate)