More Unicode support added (though untested and still unfinished).

More Unicode support added (though untested and still unfinished).
Changed code to demonstrate the new wxDbConnectInf class
ODBC environment handle now managed via the wxDbConnectInf class
Condensed the use of multiple wxDbConnectInf instances to one and got rid of the bogus EXTERNs of the wxDbConnectInf that were causing so many headaches and mismatched usages of them.
Other minor bug fixes - still have not foudn the reason for the crash on exit

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@9277 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775