Patch 1173507 by Stas Sergeev. Allow FindFirst to work with patterns

Patch 1173507 by Stas Sergeev. Allow FindFirst to work with patterns
such as 'file:abc.zip#zip:/xyz/*' that have a '/' after the 'zip:' since
it is possible to open paths such as 'file:abc.zip#zip:/xyz/123.txt'. Also
allow 'abc.zip#zip:' and 'abc.zip#zip:/' to match the zip's root. And
create a new instance of wxFileSystem within OpenFile to avoid infinite
recursion.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@33445 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775