Help needed testing automatic win64 configuration

[Brad Anderson]

Fifth and hopefully final version. Not much changed. I put this 
together so it represented the final iteration of my changes that 
will be going into pull requests.

I stopped it from downloading a modified dmd2beta.zip (because of 
the licensing issue I'd forgotten about) and just download the 
original and move phobos64.lib and gcstub64.obj to lib64 in the 
installer.  DMD now supports (as of 2.064 beta 2) LINKCMD in 
Environment64 so I no longer need dmd changes.

http://gnuk.net/dmd-2.064-beta-new-sc.ini-5.exe

People using Visual Studio Express 2010 and Windows SDK 7.0A: 
Sorry, couldn't think of a good solution for that combo.

Thanks to everyone who helped me test.

Relevant pull requests:
https://github.com/D-Programming-Language/dmd/pull/2684
https://github.com/D-Programming-Language/phobos/pull/1652
https://github.com/D-Programming-Language/installer/pull/22 
(putting some finishing touches on this in a moment then calling 
it good)