configure branch and windows port

I did some work in the "configure" branch:

----- catch up, fix some bit-rot, stuff that should have changed with
the split build but didn't yet.

Among the changes here:
	- "make date" updates patchlev.h
	- "make checkin" now does a git commit, updating patchlev.h.
	- fix "make header-check"



----- "mingw" windows port.  There are changes, mostly to the
"Make2.mingw" files to fix so it now compiles with the split build.
Also, some other files have changed to fix windows-specific problems
and errors that showed because of differences between windows and posix.

This is set up to cross-compile on a unix system with mingw.  It
compiles for me, but I could not test it to see how it actually runs,
probably because of misconfiguration of wine on my own system.  Before
pushing it to unstable, and eventually to master, I need help testing.
Can someone test it on a real windows system and tell me how it works
or doesn't work?




Some notes on the antique build system ....

This is a "recursive make", in spite of claims by some that recursive
make is bad.  It's good here, because it presents the parts separately,
so they can be built separately.

Refresher ..
-- "include" is the header files, ready to install as is.
-- "lib" is the core library, used by various programs
-- "main" and "modelgen" are two programs that use the library.
The build system here can be used as a prototype for other programs
that use the library.  Just change Make1.  The build related files
except for Make1 are identical in both of these directories.
-- "apps" is a package of plugins.  In this case, it is the package of
plugins loaded by default.  The build system here can be used as a
prototype for other plugin packages.  Just change Make1.

Before merge and release, I plan to put the Make2* and Make3* in
include, so they are installed with the headers, to facilitate building
plugin packages.


still looking at libtool branch.