Minor entrybox cleanup, and entry text has now no max size limit.

src/entrybox.cc

@@ -92,6 +92,7 @@ void EntryBox::clear() {
 void EntryBox::show() {
   std::vector<Gtk::Widget*> focus_chain;
   for(auto& entry: entries) {
+    entry.set_max_length(0);
     lower_box.pack_start(entry, Gtk::PACK_SHRINK);
     focus_chain.emplace_back(&entry);
   }

src/window.cc

@@ -741,6 +741,7 @@ void Window::goto_line_entry() {
       }
     });
     auto entry_it=entry_box.entries.begin();
+    entry_it->set_placeholder_text("Line number");
     entry_box.buttons.emplace_back("Go to line", [this, entry_it](){
       entry_it->activate();
     });
@@ -776,6 +777,7 @@ void Window::rename_token_entry() {
           }
         });
         auto entry_it=entry_box.entries.begin();
+        entry_it->set_placeholder_text("New name");
         entry_box.buttons.emplace_back("Rename", [this, entry_it](){
           entry_it->activate();
         });