debugger: don't hang on ^d and ^c

lib/_debugger.js

@@ -595,7 +595,7 @@ function Interface() {
     self.handleSIGINT();
   });
 
-  term.on('close', function() {
+  term.on('attemptClose', function() {
     self.tryQuit();
   });
 

lib/readline.js

@@ -314,6 +314,17 @@ Interface.prototype._historyPrev = function() {
   }
 };
 
+
+Interface.prototype._attemptClose = function() {
+  if (this.listeners('attemptClose').length) {
+    // User is to call interface.close() manually.
+    this.emit('attemptClose');
+  } else {
+    this.close();
+  }
+};
+
+
 // handle a write from the tty
 Interface.prototype._ttyWrite = function(b) {
   switch (b[0]) {
@@ -324,13 +335,13 @@ Interface.prototype._ttyWrite = function(b) {
         this.emit('SIGINT');
       } else {
         // default behavior, end the readline
-        this.close();
+        this._attemptClose();
       }
       break;
 
     case 4: // control-d, delete right or EOF
       if (this.cursor === 0 && this.line.length === 0) {
-        this.close();
+        this._attemptClose();
       } else if (this.cursor < this.line.length) {
         this.line = this.line.slice(0, this.cursor) +
                     this.line.slice(this.cursor + 1, this.line.length);