Add file/line information to named events and better expr. error.

This patch adds file and line number information to named events.
It also modifies the draw_eval_expr_wid() routine to fail with
an appropriate message for named events. This checking needs to
be pushed into the elaboration stage, but this will give a better
message than we had before.
(cherry picked from commit dff6a1ebff)

t-dll-expr.cc

@@ -308,6 +308,7 @@ void dll_target::expr_event(const NetEEvent*net)
       assert(expr_);
 
       expr_->type_ = IVL_EX_EVENT;
+      FILE_NAME(expr_, net);
       expr_->value_= IVL_VT_VOID;
 
         /* Locate the event by name. Save the ivl_event_t in the

tgt-vvp/eval_expr.c

@@ -2983,6 +2983,12 @@ struct vector_info draw_eval_expr_wid(ivl_expr_t exp, unsigned wid,
 	    res.base = 0;
 	    res.wid = 0;
 	    break;
+	  case IVL_EX_EVENT:
+	    fprintf(stderr, "%s:%u: vvp-tgt error: A named event is not "
+	                    "handled in this context (expression).\n",
+	                    ivl_expr_file(exp), ivl_expr_lineno(exp));
+	    exit(1);
+	    break;
 
 	  case IVL_EX_STRING:
 	    res = draw_string_expr(exp, wid);