Add 2.5 MSI builder.

Tools/buildbot/buildmsi.bat

+@rem Used by the buildbot "buildmsi" step.
+
+cmd /c Tools\buildbot\external.bat
+@rem build release versions of things
+call "%VS71COMNTOOLS%vsvars32.bat"
+if not exist ..\db-4.4.20\build_win32\release\libdb44s.lib (
+   devenv ..\db-4.4.20\build_win32\Berkeley_DB.sln /build Release /project db_static
+)
+
+@rem build Python
+cmd /q/c Tools\buildbot\kill_python.bat
+devenv.com /useenv /build Release PCbuild\pcbuild.sln
+
+@rem fetch the documentation
+python Tools/buildbot/getchm.py
+
+@rem buold the MSI file
+cd PC
+nmake /f icons.mak
+cd ..\Tools\msi
+del *.msi
+nmake /f msisupport.mak
+%HOST_PYTHON% msi.py

Tools/buildbot/getchm.py

+# We cannot build the documentation on Windows, so download an old
+# one instead.
+import urllib, os
+if not os.path.exists("Doc/python25.chm"):
+    urllib.urlretrieve("http://www.python.org/ftp/python/2.5.1/Python25.chm",
+        "Doc/python25.chm")