Bump Windows "build number" to 6.

Note that somebody still needs to change the interpreter to say "2.0b2";
I'm assuming that's a normal part of somebody's Unix release checklist.

PCbuild/BUILDno.txt

@@ -33,6 +33,8 @@ How to change the Windows build number:
 
 Windows Python BUILD numbers
 ----------------------------
+   6    2.0b2
+        26-Sep-2000
    5    CVS development
         07-Sep-2000
    4    2.0b1 repaired to include Lib\xml + Lib\lib-old + Lib\test\*.xml

PCbuild/python20.dsp

@@ -694,11 +694,11 @@ SOURCE=..\Modules\getbuildinfo.c
 
 !IF  "$(CFG)" == "python20 - Win32 Release"
 
-# ADD CPP /D BUILD=5
+# ADD CPP /D BUILD=6
 
 !ELSEIF  "$(CFG)" == "python20 - Win32 Debug"
 
-# ADD CPP /D BUILD=5
+# ADD CPP /D BUILD=6
 
 !ELSEIF  "$(CFG)" == "python20 - Win32 Alpha Debug"