Argh!  Wait!  We've gone through weeks (possibly months) of pain trying to resolve the _USE_32BIT_TIME_T issue.  Anything involving that define affects more than just MSVC builds, and more than just building the Tcl core.  Please consider any change _very_ carefully.  Jan Nijtmans and I (to a lesser extent) can provide more background.

It's not clear to me what you mean with resolving the _USE_32BIT_TIME_T issue, as tclWinPort.h starts with setting it.