(Usability improvement) Implement half-second wait for user to finish typing before...

(Usability improvement) Implement half-second wait for user to finish typing before searching packages

commit 357c1e7576586349efb8514dc9d8d03950e225ee
Author: Ronald Ramos <ronjoe223@gmail.com>
Date:   Mon Aug 1 23:05:44 2016 -0400

    * proppage.h (PropertyPage)
        New member OnTimerMessage (delegates similarly to OnMouseWheel)

    * proppage.cc
        (DialogProc) Added handling of WM_TIMER

    * choose.h (ChooserPage)
        (OnTimerMessage) New function prototype
        (timer_id) New member variable
        Added DEFINE-ed default values for timer_id and search timer delay
        Reorganized private members for consistency

    * choose.cc
        (constructor) Initialize timer_id
        (OnMessageCmd) Replaced search-refresh with a SetTimer
        (OnSearchTimer) New; contains search-refresh removed from OnMessageCmd