Git based tag builds (win32)

[Geert Janssens]

Just for your information, I have pushed a couple of changes to the 
repository that will change the tag build behaviour on our windows build 
server:

- all (new) tags starting from 2.5.0 will from now on be built from a git 
repository
- all (new) tags for the 2.4 series continue to be built from svn as it was.

I have tested this yesterday on the build server and it seems to work 
fine. But do keep this in mind should the 2.5.2 installer for Windows fail 
to upload in a couple of weeks.

This brings us one step closer to a fully git based workflow. The known 
remaining items to fix are listed on 
http://wiki.gnucash.org/wiki/Git_Migration#List_of_things_to_be_done

Geert