#501 Update VC makefile for Threads (Fix for bug 1643367)

[Twylite]

The attached patch updates the makefile.vc and rules.vc to be in line with the sampleextension in CVS (plus the changes I have submitted in bug [ 1689286 ] nmakehlp not building on Win32 with VC).

It also acts as a fix to bug [ 1643367 ].

Tested with VC6 and VC8 on Windows 2000. Builds, installs and runs correctly (including running all tests), so far as I can tell ;)

There are a number of changes:
- configure.in: note to change DOTVERSION in makefile.vc when you update the version
- win/thread.rc: the sampleextension makefile.vc provides different variables/defines to rc
- tests/thread.test: tcl_PatchLevel ==> tcl_patchLevel
- win/makefile.vc, win/nmakehlp.c and win/rules.vc: added, based on sampleextension with minimal changes needed to make it work with threads extension

The files win/vc/makefile.vc, win/vc/nmakehlp.c, win/vc/pkg.vc and win/vc/rules.vc are no longer required and should be deleted. They have effectively been moved to win/ and replaced with updates based on
sampleextension. If these files stay in win/vc and get modified to be in a "non-standard" location, then we ensure this pain every time they need to be updated (otherwise we just copy from sampleextension).

[Twylite]

Thread patch for VC8 (Twylite, 2007/03/27)