Pared down tclZipVfs to eliminate #ifdef branches that we don't have to worry
about with a modern Tcl.

Replaced dummy calls to VFS with NULL 

Where practical, replaced string-based Tcl IO calls with their new obj-based
successors. (Tcl_FSOpenChannel, Tcl_FSStat, etc)

Eliminated compiler warnings under Windows
Added a hac^H^H^Hpatch from ferrieux to mask around the exit hang on windows until
the issues are fixed at the core level.
Merging in changes from core_zip_vfs