Don't dismiss code hints on key up events except for Home and End keys.

This fixes an issue for @dloverin who needs to show function hints with Ctrl+Shift+Space shortcut. 

This also fixes some remaining issues in #2539 which can be reproduced with typing ``$`` on French keyboard layout that requires user to press Option+5 keys on Mac. When typing ``$`` with English keyboard layout in a JavaScript file, you will see code hints showing $. When trying with French keyboard layout on Mac, the code hint list pops up and then immediately dismissed.