regression: cross-arch drconfig from 32-bit to 64-bit on Windows fails with file configs

_From [rnk@google.com](https://code.google.com/u/rnk@google.com/) on September 19, 2012 05:31:34_

This came up while porting drconfig to Linux in issue #840 . From the comments https://codereview.appspot.com/6496077/diff/14/tools/drdeploy.c#newcode935 :

"""
When I do "drconfig.exe -64" for some app, I still get a
.config32 file in ~/dynamorio.

If I understand it correctly, the definition is in utils.c, which is linked into
drconfiglib and policy_static, both of which are linked against by drconfig.exe.
drconfiglib is a dll and policy_static is, well, static. So this call goes to
policy_static and sets a global variable there. Then drconfiglib calls
get_dr_platform, which resolves internally, and reads it's own global variable,
which gets the default for however drconfig is built.
"""

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=900_