`win-versioninfo': all builds of all Windows binaries now contain

`win-versioninfo': all builds of all Windows binaries now contain
a VERSIONINFO resource. The versioning scheme is described in
windows/version.rc2.

Some .rc files are now #included in others. In order to keep MSVC
project files working, these have been renamed to .rc2; there may exist
a better solution.

(This checkin also includes the documentation tweak missing from r6367.)

Testing performed:
 - MinGW (cross-compiler): works
 - VC nmake: works (tested with VC6)
 - VC project files: builds with VERSIONINFO resource (no VER variable though)
 - Borland: an old version of this patch was tested with it and more or
   less worked, except that some of the VERSIONINFO strings were apparently
   not terminated properly. Not attempted to work around this.
 - LCC: not tested. Some fixes are in there from the last time we tried
   this, but then the build ultimately failed and I haven't tried this
   since that was fixed.
 - Dev-C++: untested. (Haven't done anything special.)
 - Unix Gtk/autoconf Makefiles work as before.

git-svn-id: svn://svn.tartarus.org/sgt/putty@6374 cda61777-01e9-0310-a592-d414129be87e