Instead of performing the search only up to a certain number of items, do it
for as long as it takes less than the given time threshold (currently fixed at
half a second).
Closes#13038.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67227 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775