Added support for dBase, PostGres, MySQL, Access, MS SQL Server.

Added support for dBase, PostGres, MySQL, Access, MS SQL Server.
Added QUERY_ONLY data connection types.
SQL logging code addded.
Cleaned up handling compilation under both 1.6x and 2.x.
Added debug code to warn when connections were not released on program termination.
MS-VC6 corrections due to larger memory buffers required.
Parameter added to not require CreateView() and CreateTable() to drop the view or table first.
DropView() function added.
Database UserIDs can now be passed to functions that need them.
SQLUnbind() called where needed now to prevent resource leaks.
TableExists() function now handles dBase files.
Dbms() function added to determine which database the program is currently running against.
Comments have been added to the Dbms() function to indicate issues specific to different data sources.
Dynamic cursor support added (no longer creates 5-7 cursors for every wxTable instance).
wxTable dtor is now virtual.
Parameter added to not require CreateIndex() and CreateTable() to drop the view or table first.
DropIndex() and DropTable() functions added.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@3868 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775