regen/embed.pl: Generate ARGS_ASSERT in more cases

This macro is actually always generated, but is empty if there are no
assertions needed.

But unntil this commit the code could wrongly create an empty macro.
This happened unless at least one of the arguments to the function was
marked NN.

Author: khwilliamson

proto.h

@@ -359,7 +359,7 @@ sub generate_proto_h {
 
         if ($args_assert_line) {
             $ret .= "\n#${ind}define PERL_ARGS_ASSERT_\U$plain_func\E";
-            if (@names_of_nn) {
+            if (@names_of_nn || @typed_args) {
                 $ret .= " \\\n";
 
                 my @asserts;