swc-windows-installer.py: Add missing space to 'c:\ProgramFiles'

This is the default for when ProgramFiles isn't set.  Windows
operating systems should always have that environment variable set, so
the default is probably only useful when you're testing the script on
a non-Windows system.
swc-windows-installer.py: Search ProgramW6432 and ProgramFiles(x86)

It turns out that the 'ProgramFiles' environment variable is set
differently depending on the architecture of process in question.  To
always get the 32-bit x86 version, you should use 'ProgramFiles(x86)'
[1].  To always get the 64-bit amd64 version, you should use
'ProgramW6432' [2].

To be safe, and support both 32- and 64-bit Windows installs, just
search everything that could be relevant.  Prefer 64-bit locations
(when we have any).

[1]: http://technet.microsoft.com/en-us/library/cc749104%28v=ws.10%29.aspx
     Recognized Environment Variables
     ...
     CSIDL_PROGRAM_FILES  Version 5.0. The Program Files folder.
                          A typical path is C:\Program Files.
     ...
     PROGRAMFILES         Same as CSIDL_PROGRAM_FILES.
     PROGRAMFILES(X86)    Refers to the C:\Program Files (x86) folder on
                          64-bit systems.

[2]: http://msdn.microsoft.com/en-us/library/windows/desktop/aa384274%28v=vs.85%29.aspx#Environment_Variables
     WOW64 Implementation Details
     ...
     64-bit process:
        ProgramFiles=%ProgramFiles%
        ProgramW6432=%ProgramFiles%
     32-bit process:
        ProgramFiles=%ProgramFiles(x86)%
        ProgramW6432=%ProgramFiles%

     The ProgramW6432 and CommonProgramW6432 environment variables
     were added starting with Windows 7 and Windows Server 2008 R2.