TDBC

As a follow-up to [Tcl FRQ 3010352],

Objective: simplify Stubs by

- exporting only the minimally needed symbols, i.e.
only Tdbc_Init, nothing more.

- Eliminate the need for -DUSE_TDBC_STUBS

For TclOO, this is already done, I have a
corresponding patch for Tdbc available.

<hr /><i>anonymous added on 2011-11-07 10:05:24 UTC:</i><br />
Implementation available now in branch rfe-b4029dc351

Kevin, is this suitable for the next beta?

            Jan Nijtmans

<hr /><i>jan.nijtmans added on 2012-06-10 20:11:21 UTC:</i><br />
Now tested on Windows and UNIX, should work fine on all platforms