swc-installation-test-2.py: Use ProgramFiles environment variable

On Fri, Apr 26, 2013 at 11:45:12AM -0700, Onno Broekmans wrote:
> ... the installation paths you mention are incorrect for the
> majority of modern Windows 7 installations. These are 64-bit
> installations, and they have a special folder for 32-bit programs:
> "C:\Program Files (x86)". So Notepad++ can be found in:
>
>     C:\Program Files (x86)\Notepad++\notepad++.exe
>
> In the script, you could just check for the program's existence
> using both paths ("C:\Program Files" _and_ "C:\Program Files
> (x86)"), or you could use the "ProgramFiles" environment variable.

Environment variable it is!  From the Microsoft docs [1]:

  CSIDL_PROGRAM_FILESX86
    The Program Files folder on 64-bit systems. A typical path is
    C:\Program Files(86).
  ...
  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.

We're just looking for executables, so it would be ok if we found a
32-bit Notepad++ or a 64-bit Notepad++.  With this commit, we check
both locations (if there are two distinct locations).

[1]: http://technet.microsoft.com/en-us/library/cc749104%28v=ws.10%29.aspx